Graft copolymers and blends thereof with polyolefins

ABSTRACT

A novel graft copolymer capable of imparting to a polyolefin when blended therewith high tensile modulus and high sag resistance without increasing melt viscosity, and a method of making the same. The graft copolymer is a polyolefin having a relatively high weight-average molecular weight methacrylate polymer grafted thereto. The graft copolymer is formed by dissolving or swelling a non-polar polyolefin in an inert hydrocarbon solvent, heating to dissolve the polyolefin, and while stirring the mixture, adding a methacrylate monomer, together with an initiator to produce a constant, low concentration of radicals, to form a graft copolymer with a high molecular weight polymer chain covalently bonded or grafted to the polyolefin backbone. The graft copolymer can be separated from the solvent, isolated by volatilizing the solvent, for example in a devolatilizing extruder, and extruded into a desired shape such as a sheet, tube or the like. This graft copolymer can be blended with a polyolefin matrix. The blend exhibits improved physical properties in the melt, upon cooling, and in the solid state, and is useful in cast and oriented films, solid extruded rod and profile, foamed rod, profile and sheet, blown bottles and the like. The graft copolymer further improves compatibility in a wide range of polymer blends.

This is a continuation-in-part of Ser. No. 174,648, filed Mar. 29, 1988and now abandoned.

FIELD OF THE INVENTION

This invention relates broadly to a novel graft copolymer capable ofimparting to a polyolefin, when blended therewith, high tensile modulusand high resistance to sagging without increasing melt viscosity, and toa method of making the same.

More particularly, the invention relates to a polymerized olefin havinggrafted thereto, by covalent bonding, a polymeric methacrylate chain ofrelatively high molecular weight. The methacrylate chain has a weightaverage molecular weight (M_(w)) of at least 20,000 and advantageouslybetween about 30,000 and 150,000.

In the method of manufacturing the grafted copolymer, a non-polarpolyolefin, preferably polypropylene or polyethylene, is introduced intoan inert hydrocarbon solvent which dissolves (or swells) the polyolefin,by heating to a temperature at which the polyolefin is dissolved. Whileagitating the solution, methyl methacrylate (MMA) monomer, together withan initiator which generates a constant, low radical flux concentrationsufficient to initiate polymerization of the monomer at the temperatureof the solution and the formation of the covalent bond, is graduallyadded. The polyolefin with a side-chain grafted thereto is thereafterseparated from the solvent by volatilizing the solvent, preferably in adevolatilizing extruder. The graft polymer is then blended with asuitable polyolefin such as polypropylene or polyethylene, and extrudedinto a desired shape.

BACKGROUND OF THE INVENTION

Non-polar polyolefins, especially polypropylene and polyethylene andmixtures in various low-density, high-density, and linear low-densityform, are major articles of commerce for a wide variety of uses.Nevertheless, there exist specialty needs for which the marketplace hasnot provided a satisfactory answer. Among these are to overcome thedifficulty of thermoforming and processing of the polyolefin, especiallyunfilled, in a molten or semi-molten form (substantially above itsmelting point); the polymer tends to sag readily under its own weightbecause it exhibits an undesirably low stiffness, and to form shapes ofgrossly non-uniform thicknesses upon thermoforming. Attempts to correctsame by increasing the molecular weight lead to difficulties inprocessing the higher molecular weight polymer not encountered with thelower molecular weight grades.

For the isotactic polymer of butene-1, known also as polybutylene, thelow melting point has made difficult the crystallizing of the polymerafter processing and obtaining the enhanced performance and handlingproperties crystallization imparts. Satisfactory nucleators have notappeared in the marketplace.

Means have also been sought to improve the toughness or impact strengthof polypropylene, for instance. Use of copolymers or ethylene-propylenerubber modified polypropylene has improved toughness, but at the cost ofeven lower stiffness values, and lower values of heat distortionresistance. It would be desirable to combine impact performance of thecopolymers with stiffness and heat distortion behavior of thehomopolymer polypropylene resin.

Grafting of monomers capable of vinyl polymerization, such as styrene,methyl methacrylate, and the like, onto polyolefins such aspolyethylene, polypropylene, ethylene-propylene copolymers, andethylene-propylene-diene terpolymers has been studied almost since thediscovery of routes to practical preparation of such backbones. Graftingonto solid polymer by vapor-phase polymerization, by reaction in anextruder, by peroxidation of the olefinic backbone, and grafting ontopendant double bonds are all routes which have been attempted. Therestill exists a need for a route which allows for grafts of relativelyhigh molecular weight, with relatively good grafting efficiency (i.e.,lowered formation of unattached polymer molecules), freedom from gel,and a practical means for preparing and isolating the graft polymer inan efficient and lower-cost manner.

Blends of two or more polymers have often been made, for example inattempts to combine desirable properties of the individual polymers intothe blend, to seek unique properties in the blend, or to produce lesscostly polymer products by including less expensive or scrap polymers inthe blend. Compatible polymers tend to form blends that contain smalldomains of the individual polymers; in the case of "miscible" polymersthese occur at the molecular scale, resulting in properties usuallyconsidered characteristic of a single polymer. These may includeoccurrence of a single glass-transition temperature and optical clarity.Such blends are frequently termed "alloys." Compatible polymers that arenot strictly miscible, as described above, nevertheless tend to formblends with properties that approach those of the miscible blends. Suchproperties as tensile strength, which rely upon adhesion of the domainsto one another, tend not to be degraded when compatible polymers areblended.

Unfortunately many polymers are poorly compatible with one another. Poorcompatibility cannot necessarily be predicted accurately for a givenpolymer combination, but in general it may be expected when non-polarpolymers are blended with more polar polymers. Poor compatibility in ablend is apparent to those skilled in the art, and often evidencesitself in poor tensile strength or other physical properties, especiallywhen compared to the component polymers of the blend. Microscopicevidence of poor compatibility may also be present, in the form oflarge, poorly adhered domains of one or more polymer components in amatrix of another polymer component of the blend. More than oneglass-transition temperature may be observed, and a blend of otherwisetransparent polymers may be opaque because the domain sizes are largeenough to scatter visible light.

Much research has been directed toward finding ways to increase thecompatibility of poorly compatible polymers when blended. Approachesthat have been used include adding to the blend polymers which showcompatibility with the other, mutually incompatible polymers; such addedpolymers act as a bridge or interface between the incompatiblecomponents, and often decrease domain size. Chlorinated polyethylene hasbeen used as such an additive polymer, especially in blends ofpolyolefins with other, poorly compatible polymers.

Graft polymers, as of incompatible polymers A onto B, are known to aidin blending polymers A and B. Such graft polymers may also serve to aidin blending other incompatible polymers C and D, where A and C arecompatible and B and D are compatible.

What has also been difficult to predict in polymer science is the extentto which such a graft polymer will be effective in enhancing desirableproperties of the blend over those of the incompatible blend alone.Consequently, those skilled in the art have had to treat eachcombination of graft polymer and other component polymers of a givenblend as a special case, and determine experimentally whether animprovement in such properties as tensile strength could be obtained byadding a specific graft polymer to a specific blend.

RELEVANT ART

U.S. Pat. No. 4,094,927 describes copolymers of higher alkylmethacrylates with (meth)acrylic acid as melt strength additives, foamstabilizers, and processing aids for polypropylene. Such polymers,however, are not fully compatible with polypropylene and the additivewill tend to plate out and foul equipment during such operations as meltcalendering.

U.S. Pat. No. 4,409,345 describes polyolefin modified with apolymerizable unsaturated carboxylic ester in affording improvedprocessing of mixtures of polypropylene, high density polyethylene, andfinely divided vegetable fibers. The patent appears only to demonstratereinforcement by the fibers which are bonded to the polyolefin by thegraft copolymer. All examples are limited to "grafts" of maleicanhydride or acrylic acid, wherein the material grafted is of amolecular weight corresponding to a small number of monomer units.

South African Patent No. 826,440 describes "improved melt viscosity"(higher melt viscosity under low shear conditions while retaining thelow melt viscosity at high shear rheology behavior of the unmodifiedpolypropylene) and improved thermoforming characteristics for blends ofpolypropylene with certain salts of acid-modified propylene polymers.

U.S. Pat. No. 4,370,450 describes modification of polypropylene withpolar vinyl monomers by polymerization in aqueous suspension containinga swelling agent at temperatures above 85° C. with a radical chaininitiator having a half-life of at least 2 hours in the temperaturerange 80°-135° C. The patent does not describe direct solution grafting,stating such yields "only relatively low degrees of grafting".Hydrocarbons are listed as examples of swelling agents.

U.S. Pat. No. 4,161,452 describes only grafts of unsaturated carboxylicacids or anhydrides and esters of (meth)acrylic acid ontoethylene/propylene copolymers in solution in the presence of afreeradical initiator capable of hydrogen abstraction at temperaturesbetween 60° and 220° C. An oil soluble polymer is required.

U.S. Pat. No. 4,595,726 describes graft copolymers of C₂ -C₆ alkylmethacrylates onto polypropylene via a solvent-free vapor-phasepolymerization wherein the molecular weight of the graft and the numberof grafted chains are controlled to yield the desired (althoughundefined) length and number of chains for utility in adhesiveapplications between polypropylene and more polar substrates. The patentdiscloses that similar grafts can be made from methyl methacrylate, butdo not exhibit the desired adhesive properties. The patent requirespolymerization below the softening point of polypropylene, which is notdefined in their patent, which is known to be lowered by the presence ofmonomers, and for which no temperature higher than 140° C. isexemplified, and in the absence of solvent. There is no indication orsuggestion that a relatively high molecular weight chain is covalentlygrafted to the polyolefin. Moreover, the radical flux generated appearsto be too high to form a high molecular weight, e.g. greater than20,000, chain.

U.S. Pat. No. 4,692,992 describes grafting at temperatures between 60°and 160° C. while maintaining the olefin polymer dissolved in a solventwhich is a mixture of a hydrocarbon and a ketonic solvent, the graftedpolymer precipitating upon cooling the reacted mixture below 40° C.Reaction conditions for achieving high molecular weight or the advantagein conducting the reaction in the presence only of a solvent of lowchain transfer activity are not disclosed.

U.S. Pat. No. 3,862,265 only describes melting of polyolefins in anextruder, followed by grafting of unsaturated acids to achieve "improvedrheology" as defined in South African Patent No. 826440, supra.

U.S. Pat. No. 3,886,227 discloses (but does not exemplify for theesters) grafting of unsaturated acids and esters to form a materialuseful as a modifying agent for polypropylene. The grafting is conductedin an extruder, and they also disclose that the molecular weight of thebackbone polypropylene polymer be lowered by degradation during thegrafting process, conducted at a temperature above 200° C. It describesblending with polypropylene and the resulting modification found, suchas nucleation, lack of warpage on molding, and the like. Althoughimprovement in heat distortion temperature is noted, there is nodisclosure of improved rheological performance at the temperaturesrequired for thermoforming and the like.

Japanese Kokai 59-164347 describes grafts for unsaturated acids or theirderivatives (including esters) at very low graft levels (10-5 to 10-8 gequivalents per gram of polyolefin), blends of the grafts withpolyolefins, and their use in affecting surface tension in the moltenstate of the polyolefin while not affecting high-shear viscosity, makingthe blends useful in, e.g. blow molding of bottles.

Kallitis et al., Eur. Polymer J., 27, 117 (1987) describesethylene-propylene polymers as nucleating agents for polybutylene. Theydo not describe or suggest the utility of the polypropylene/methacrylicgrafts of this invention.

Reike and Moore, in U.S. Pat. No. 2,987,501, disclose grafts of polymersof vinyl monomers onto polyethylene or polypropylene by oxidizing thepolyolefin with fuming nitric acid or nitrogen tetroxide, followed byheating the activated polyolefin with the vinyl monomer. The referenceexemplifies grafting methyl methacrylate onto polyethylene andpolypropylene.

Japanese Kokai 223250/87 discloses compatibilizing a polyolefin and apolyamide using a reaction product of an unsaturated carboxylic acid orits derivative grafted onto a mixture of polyolefin and polyamide, thatis, the reaction product is formed in the presence of a mixture of twoor more polymers. The amount of acid or derivative reacted with thetrunk polymers is less than 10%, and it is clear from the only examplespresent, which utilize unsaturated acids which do not homopolymerize,that what is attached or grafted are low-molecular-weight moieties,.They disclose reaction conditions, including relatively low levels ofunsaturated acid and relatively high levels of peroxide, which wouldlead one away from achieving the molecular weights of the grafted chainsdisclosed below as part of the present invention. A particular modifierdisclosed by this reference, formed by reacting two non-polymerizableacids with a mixture of four trunk polymers, affects the compatibilityof the polyamide and polyolefin. However, the comparative data suggestthat a reaction of the acids onto polypropylene alone is not aneffective compatibilizer for the two resins, and shows that graftpolymers of low levels of low molecular unsaturated acids or derivativesare not effective in compatibilizing polyamides with polyolefins.

Japanese Kokai 86040/87 directed to polymer adhesives, discloses anolefin polymer adhesive modified with a carboxylic or carboxylicanhydride group, further reacted with a polyolefin having alcoholfunctionality, and still further reacted with an aromatic acid halide.

Boutevin et al., in Angewandte Makromolekular Chemie, Vol. 162, page 175(1988), disclose the preparation of a graft polymer of poly(methylmethacrylate) onto a polyethylene trunk by ozonolysis of a low-densitypolyethylene followed by heating the activated polyethylene in thepresence of methyl methacrylate. They disclose grafts of methylmethacrylate having a number-average molecular weight up to 21400, andthe use of such grafts as polymeric emulsifiers or compatibilizers formixtures of low-density polyethylene and poly(vinyl chloride). Theyreport that the compatibilized mixture has a distinct increase in thestress required to break it, and a decrease in the domain sizes in theblend. They also report appreciable degradation of the polyethylenemolecular weight when it is ozonized prior to grafting. This referencedoes not deal with higher molecular weights, nor does it provide anyindication that the graft polymer might be effective in reducing sag ofa polyolefin matrix polymer or otherwise imparting desirable rheologicaleffects to a polymer.

Thus, the art has described means for preparing grafts of methylmethacrylate homo- and copolymers upon polyolefin substrates, but hasnot recognized the advantages of the polymerization process hereindescribed for a rapid, efficient production of novel high molecularweight grafts without gel and with ease of product isolation. The artteaches that certain grafts may be blended with polyolefins, but has notrecognized the unexpected utility of the novel graft polymers of thisinvention as having positive effects on both low-shear melt andsolid-state properties, especially with little or no effect on thehigh-shear performance. The art also has not recognized or identifiedthe positive effects on sag resistance imparted by the present grafts.

It is thus an object of this invention to provide an improved processfor the manufacture of novel graft polymers of methacrylic esters ontopolyolefin substrates. Another object is to provide graft copolymers ofat least one chain of methacrylate polymer of relatively high molecularweight, i.e. at least 20,000, onto a polyolefin homo- or copolymersubstrate. Yet another object is to provide such graft copolymers whichserve as compatibilizing agents for blends of polymers which areotherwise poorly compatible. It is a further object to provide blends ofthe graft copolymer with a polyolefin matrix which exhibit improvedphysical performance in the melt, upon cooling, and in the sold state.

Further objects and advantages of this invention will appear as thisspecification progresses.

SUMMARY OF THE INVENTION

Broadly, the aforesaid objects and advantages are accomplished bygrafting onto a non-polar polyolefin trunk in solution, at least onechain which is of a polymer having a weight average molecular weightgreater than about 20,000, and present in a weight ratio with thepolyolefin of from about 1:9 to 4:1. The graft polymer is derived fromat least about 80% of a monomer of a methacrylic ester of the formulaCH₂ ═C(CH₃)COOR, where R may be alkyl, aryl, substituted orunsubstituted, and less than 20%, based on the total monomer weight, ofan acrylic or styrenic monomer copolymerizable with the methacrylicester. This is accomplished by adding the methacrylate monomers to asolution of the polyolefin together with an initiator which generates aconstant, low radical concentration, or radical "flux", at the solutiontemperature. These radicals initiate polymerization of the monomer andcause formation of a covalent bond with the trunk.

The resulting copolymer product, hereinafter referred to as concentrate,may be blended with polyolefin either as a result of the manner by whichit is made, or after it is made. It may be extruded into a desired shapeeither directly, or after pelletization. In either case, the resultingblended product exhibits a relatively high tensile modulus and high sagresistance without an increase in melt viscosity, as compared withsimilar ungrafted polymers, viz: polyolefins without a high molecularweight chain or chains covalently bonded thereto.

The concentrate may also be blended with other polymers thanpolyolefins, and particularly with mixtures of two or more polymerswhich are poorly compatible with one another, and which may or may notinclude polyolefins, to improve the compatibility of the resultingmixture.

The invention also relates to a process of making such a copolymerhaving a relatively high weight-average molecular weight (M_(w)) polymerchain. Briefly, the process according to this invention involvesdissolving or swelling the polyolefin in an inert hydrocarbon solvent,and heating to dissolve the polyolefin, i.e. at least about 140° C.While agitating the solution, a monomer is introduced, together with aninitiator which generates a constant, low radical flux at thetemperature of the solution; the radicals initiate polymerization of themonomer and formation of a covalent bond therewith on the polyolefintrunk. The reacted mixture may be allowed to solidify by removal of thesolvent. The resultant product, the concentrate, consists of thepolyolefin with the chain grafted thereto, unreacted polymer, i.e.polyolefin without the chain, and ungrafted methacrylic ester polymer.It may be pelletized, blended with another polyolefin and extruded intodesired shape. Alternatively the reaction mixture may be extrudeddirectly in a devolatilizing extruder to volatilize the solvent andresidual monomer, and thereafter blended with a polyolefin and extrudedto form article in such form as sheets, tubes and the like.

DETAILED DESCRIPTION

In the following, LDPE is low-density polyethylene, usually branched, ofdensity of about 0.91 to about 0.94 g/cc; HDPE is high-densitypolyethylene of a density above about 0.95 g/cc; LLPDE is linearlow-density polyethylene of density about 0.91 to about 0.95 g/cc; EPDMincludes rubber terpolymers of ethylene, propylene, and a non-conjugateddiene monomer, such as 1,4-hexadiene or ethylidenenorbornene.

The term "polar substrate" or "non-polar" polymer, as used herein, isdifficult to define in quantitative terms. By "non-polar" is meantpolymers which are predominantly formed from monomer units of mono- ordi-olefins. "Polar", as generally understood in the polymer art, wouldrefer to monomers or polymers which contain an oxygen, nitrogen, orsulfur-containing functionality. Thus, methyl methacrylate,acrylonitrile, and vinyl phenyl sulfone are "polar" monomers, whereaspolypropylene is a "non-polar" polymer.

The polymers to be modified in the grafting process include thenon-polar olefin polymers and copolymers. Included are polypropylene,polyethylene (HDPE, LDPE, and LLDPE), polybutylene, ethylene-propylenecopolymers at all ratios of ethylene and propylene, EPDM terpolymers atall ratios of ethylene and propylene and with diene monomer contents upto 10%, poly(l-butene), polymethylpentene, ethylene-vinyl acetatecopolymers with vinyl acetate contents up to 25%, ethylene-methylacrylate copolymers, ethylene-methyl methacrylate copolymers, andethylene-ethyl acrylate copolymers. Also included are mixtures of thesepolymers in all ratios.

Usable graft copolymers include those with ratios of polyolefin:acrylicpolymer or copolymer that vary from 20:80 to 80:20.

The molecular weight of the polyolefin polymer which forms the trunk ofthe graft copolymer should be high enough to give a large amount ofnon-polar polymer when grafted, but low enough so that most of the graftcopolymer has one acrylic polymer chain grafted to each polyolefin trunkchain. The trunk may have a molecular weight between about 50,000 and1,000,000. The trunk may also have a molecular weight of about 100,000to 400,000. A polyolefin trunk having a molecular weight of about200,000-800,000 M_(w) is especially preferred, but polyolefins having amolecular weight of about 50,000-200,000 can be used with somebeneficial effect. In general, a graft copolymer imparts greatermeltrheology improvement to a high-molecular-weight polyolefin. This isespecially true when the polyolefin trunk of the graft copolymer is ofrelatively low molecular weight.

Melt flow rate (mfr) is well known to correlate well with weight-averagemolecular weight. The preferred range of mfr values for the polyolefintrunks used in preparing the graft copolymers of the present inventionare from about 20 to about 0.6 g/10 minutes as measured by ASTM StandardMethod D-1238.

The preferred monomer is methyl methacrylate. As much as 100% of this,or of other 2 to 4 carbon alkyl methacrylates, can be used. Up to 20% ofhigh alkyl, such as dodecyl and the like, aryl, such as phenyl and thelike, alkaryl, and such as benzyl and the like, and/or cycloalkyl, suchas cyclohexyl and the like, methacrylates can be used. In addition, upto 20% (preferably less than 10%) of the following monomers can beincorporated with the methacrylate esters which form the major portionof the monomer: methacrylic acid, methacrylamide, hydroxyethylmethacrylate, hydroxypropyl methacrylate, alkoxyalkyl methacrylates,such as ethoxyethyl methacrylate and the like, alkylthioalkylmethacrylates, such as ethylthioethyl methacrylate and the like,methacrylamide, t-butylaminoethyl methacrylate, dimethylaminoethylmethacrylate, dimethylaminopropyl methacrylamide, glycidyl methacrylate,methacryloxypropyltriethoxysilane, acrylate monomers (such as ethylacrylate, butyl acrylate and the like), styrene, acrylonitrile,acrylamide, acrylic acid, acryloxypropionic acid, vinyl pyridine, andN-vinylpyrrolidone. In addition, as much as 5% of maleic anhydride oritaconic acid may be used. It is important that the chain transfer ofthe polymerizing chains to its own polymer be minimal relative totransfer with the polyolefin chains for the efficient production ofhomogenous non-gelled graft polymer in good yield.

The molecular weight of the acrylic graft as measured by the weightaverage molecular weight of the ungrafted co-prepared acrylic polymermay be about 20,000 to 200,000. The preferred range is 30,000 to150,000.

The process of graft polymerizing the monomer leads to the production ofungrafted and grafted material. The amount of grafted material is in therange of 5% to 50% of the total acrylic polymer or copolymer produced.The graft copolymer is prepared in a process that polymerizes themonomer in the presence of the non-polar polyolefin. The process isconducted in a solvent which swells or dissolves the non-polar polymer.The solvent is also one that has no or low chain transfer ability.Examples include non-branched and branched aliphatic hydrocarbons,chlorobenzene, benzene, t-butylbenzene, anisole, cyclohexane, naphthas,and dibutyl ether. Preferably, the solvent is easy to remove byextrusion devolatilization, and therefore has a boiling point below 200°C., preferably below about 150° C. To avoid excessive pressure, aboiling point above about 100° C. is also preferred.

The final solids content (which includes polyolefin and acrylic polymer)depends on the viscosity and the ability to mix well. The practicallimits are 20% to 70% but the solids content can be as high as isconsistent with good mixing for economy. Preferably, the solids contentfalls in the range of about 35% to about 60%.

A gradual addition or multicharge addition of the monomer is preferred.Optionally, the monomer charge need not be the same throughout, forexample, the last 0-20% may contain all of the monomer used in minoramount to concentrate that monomer in one portion of the polymer.

The temperature during the polymerization can be in the range 110° to200° C. but the preferred range is 130° to 175° C. Especially preferredis 145° to 160° C. The pressure can be atmospheric to superatmospheric,or as high as 2100 kPa or whatever is necessary to keep the reactionmixture in the liquid phase at the polymerization temperature.

The unreacted monomer concentration should be kept low during thereaction. This is controlled by balancing the radical flux and themonomer feed conditions.

For polymerization, oil-soluble thermal free-radical initiators areused. Those that work in this process are those with a one hour halflife at about 60° to about 200° C. The preferred ones have a one hourhalf life in the range 90° to 170° C. Suitable free radical initiatorsinclude peroxy initiators such as t-butyl peroxypivalate, lauroylperoxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethyl hexanoate,2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, acetyl peroxide,succinic acid peroxide, t-butyl peroctoate, benzyl peroxide, t-butylperoxyisobutyrate, t-butyl peroxymaleic acid,l-hydroxy-l-hydroperoxydicyclohexyl peroxide,1,l-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxycrotonate, 2,2-bis(t-butylperoxybutane), t-butylperoxy isopropylcarbonate, 2,5-dimethyl-2,5-bis(benzoylperoxy)-hexane, t-butylperacetate, methyl ethyl ketone peroxide, di-t-butyl diperoxyphthalate,t-butyl perbenzoate, dicumyl peroxide,2,5,dimethyl-2,5-di(t-butylperoxy)hexane, 2,4-pentanedione peroxide,di-t-butyl peroxide, 2,5,-dimethyl-2,5-di(t-butylperoxy)-hexyne-3,1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide,2,5-dimethyl-2,5-di(hydroperoxy)hexane, t-butyl hydroperoxide, t-butylcumyl peroxide, p-menthane hydroperoxide and azo-bis-isobutyronitrile.

The initiator is introduced together with the monomer during thepolymerization in a manner to maintain a fairly constant radical fluxduring most of the polymerization. This is done to achieve the correcthigh molecular weight, a high graft efficiency, the desired molecularweight distribution, and freedom from gel.

Radical flux can be defined as the calculated rate of formation of freeradicals, expressed in equivalent of radicals per liter per minute.While not being capable of being measured experimentally, this may becalculated from the known rate of decomposition of the free radicalinitiator present at any time, and its instantaneous concentration.Decomposition rates for initiators are determined from publishedliterature, and the concentration is either a known constant, as incontinuous feed of initiator, or can be calculated (for a single chargeof initiator) from the known decomposition rate constant and the timeelapsed since feed.

Good results are achieved when a uniform radical flux is maintained andthe radical flux is calculated to be in the range 0.00001 to 0.0005equivalents of radicals per liter per minute. The preferred range is0.00002 to 0.0002 equivalents of radicals per liter per minute. Theradical flux is dependent on the specific initiator utilized, itsconcentration and rate of decomposition, and the reaction temperaturechosen. The rate of decomposition can be found in tabulated data, suchas in "The Polymer Handbook", 2nd Edition, ed. Brandrup and Immergut,Wiley and Sons, N.Y. (1975), or provided by the manufacturer. Even ifthe exact rate constant at the temperature of interest is not known,often activation energies are supplied from which the rate can becalculated. The radical flux is:

    Radical flux=2(k.sub.d)(60)(I)

where k_(d) is that rate constant for decomposition of the particularinitiator in units of inverse seconds, and I the concentration of theinitiator in mol/liter. In a batch reaction, I steadily decreases fromI_(o), the initial charge, and the radical flux is not constant. Wheninitiator is continuously fed, a calculation must be made to determinethe instantaneous concentration of initiator, but the value is much moreconstant than in a batch reaction, especially with careful control ofinitiator feed.

The process may be run in a semi-continuous or continuous manner.Monomer, solvent, and initiator may be added by means similar to thosedescribed above. Polymer may be separately dissolved in solvent andadded at a rate essentially equivalent to that of product removal, orpolymer may be melted and added as a solid to the reaction by means ofan extruder.

After the polymerization, a hold time may be used. Then the mixture isdevolatilized to remove solvent and any unreacted monomer. Acceptabledevolatilizing devices include a devolatilizing extruder, a rotary filmevaporator, or any other convenient stripping device as known in theart. The polymerization reaction mixture may be conveyed to thedevolatilization apparatus as a batch or continuously.

Prior to, during, or after the devolatilization step, appropriateadditives may be admixed into the graft copolymer solution/suspensionwhich are desired to be present in the isolated graft copolymer. If suchadditives do not affect the grafting reaction, they may be added priorto, during, or after the polymerization process. Such additives may alsobe added when the graft copolymer is blended with the matrix polymer.Such additives may include stabilizers against light or heat, such asbenzotriazoles, hindered amines, alkyl polysulfides such as dialkyldisulfides, and the like, lubricants, or plasticizers; flame retardants;and the like. Preferred is the addition of a disulfide, such asdi-n-dodecyl disulfide or di-t-dodecyl disulfide and the like at levelsbetween about 0.001% to about 0.05% by weight of graft polymer, based onthe weight of graft copolymer plus matrix polymer, to stabilize theacrylic portion of the graft copolymer against thermal degradationduring melt processing while admixing into the matrix or blending andextruding.

A second class of stabilizer is thetris(polyalkylhydroxybenzyl)-s-triazinetriones. Preferred istris-(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-s-triazine-(1H, 3H,5H)-trione, at levels from about 0.001 to about 0.1% by weight, based onthe total polymer weight.

Stability may also be imparted to the acrylic portion of the graftcopolymer by including an alkylthioalkyl (meth)acrylate, preferablyethylthioethyl methacrylate, with the acrylic monomer or monomers duringthe graft polymerization.

The product is then isolated by stranding, cooling, chopping, drying,and bagging, or other known collection techniques.

The polyolefin and the graft copolymer concentrate may be blended bymixing the dry feed materials and extruding either directly to form afilm, sheet or the like, or by collecting the blend and reprocessing itinto the desired article, or by adding the polyolefin in the course ofthe devolatilization.

Polyolefins are often produced with one or more stabilizers to preventdegradation of the polymer appearance or physical properties duringprocessing and/or end use. Such stabilizers may include metal salts suchas metal stearates, which act as acid acceptors, hindered phenols, whichact as anti-oxidants, and sulfur-containing organic esters orderivatives, added as heat stabilizers. Examples of such additives,which are usually proprietary to the supplier, are metal stearates,2,6-dimethylphenolic compounds, and thiodiesters of long-chain alcohols.Polyolefins may also contain light stabilizers, such as hindered amines,benzotriazoles, and the like. All of the polyolefins used in the presentexamples are thought to contain small amounts of these proprietarystabilizers.

One way to specify the blend composition is that at least about 0.2% ofthe total formulation (polyolefin plus graft copolymer) should bechemically grafted acrylic polymer or copolymer within the molecularweight limits specified. The maximum amount is about 10% grafted acrylicpolymer, with up to about 5% grafted acrylic polymer being preferred forcost optimization and optimization of most properties of the blend.

Optionally, the blend of concentrate and polyolefin may be furthermodified by the introduction of fillers, both inorganic and organic,fibers, impact modifiers, colorants, stabilizers, flame retardants,and/or blowing agents.

Blowing agents may be gases, such as nitrogen or carbon dioxide, admixedwith the polymer melt in the extruder and allowed to expand uponextrusion. More often, blowing agents are solids which liberate gases,usually nitrogen, at a specific melt temperature, and which are mixedinto the melt, or blended from a pre-compounded mixture of the blowingagent dispersed in a polymeric matrix. The melt temperatures for thepolyolefins are typically in the range of about 200° to about 230° C.,although other temperatures may be used, depending on the specificblowing agent. Solid blowing agents include azo compounds such asazodicarbonamides, azoisobutyronitriles, hydroazo compounds, orcompounds containing the nitroso group.

The blend of the graft copolymer and polyolefin is useful inthermoforming, film making (especially blowing and extruding), blowmolding, fiber spinning, acid and basic dyeing, foaming, extrusion(sheet, pipe, and profile), coextrusion (multilayer film, sheet,preforms, and parisons, with or without the use of tie layers), hot meltadhesives, calendering, and extrusion coating (for the preparation ofpolymer/fabric, carpet, foil, and other multilayer constructions). Suchgraft copolymers, especially with small amounts of copolymerized acidfunctionality, are useful when blended with polyolefins for improvedprintability. The grafts themselves may be used as tie layers betweenotherwise incompatible polymers.

In extrusion, the graft copolymer is useful, especially with LLDPE, atreduction of melt fracture without an effect on the melt flow rate.Unlike the additives of U.S. Pat. No. 4,094,297, the present additivesdo not plate out when the modified polyolefin is extruded for extendedtimes.

When polypropylene is modified with the graft copolymers of the presentinvention, it may be employed in the manufacture of many useful objects,such as extrusion- or injection-blown bottle for packaging offoodstuffs, aqueous solutions such as intravenous feeds, hot-filleditems such as ketchup, or extruded articles in profile form such asclips, scrapers, window and door casings and the like. The foamedarticles may be used as substitutes for wood in moldings, for packagingmaterials, for insulation or sound-deadening materials, for foodcontainers, and other rigid-article applications. Films may be used inmany protective or wrapping applications, such as for food packaging,blister packaging of consumer goods, and the like.

The graft copolymers of the present invention are useful in preparingpolyolefin fibers, especially polypropylene fibers; they are especiallyuseful when the graft copolymer is formed from a polypropylene trunk.Polypropylene is relatively easy to process into fibers having highstrength and toughness.

Polypropylene fibers show certain deficiencies which include difficultyin dyeing and poor long-term dimensional stability. Grafts containingfunctional sites capable of accepting dye may be prepared by the presentprocess by incorporating low levels of dye-accepting monomers, such asmethacrylic acid, dimethylaminoethyl methacrylate, N-vinylpyridine, andthe like. The improved sag resistance noted for the present graftpolymers in a polypropylene matrix should correspond to improvements increep resistance of the fiber.

Polypropylene may be formed into fibers by sitting tape from extrudedfilm to form large-denier, coarse fibers, by extruding monofilamentsinto large-denier fibers with a controlled cross-sectional size, or byextruding multifilaments through a spinnerette to produce bundles ofsmall-denier fibers. In all cases, the fibers may be drawtextured. As anexample, small-denier polypropylene fiber bundles may be extruded from a25.4-mm, single-screw extruder having a screw length-to-diameter ratioof 24:1, such as that supplied by Killion Extruders Corp. of CedarGrove, N.J. and equipped with a static mixer, metering pump andspinnerette assembly with multiple orifices. Using such equipment theextruded polypropylene would be passed though a cooling bath and thenover a series of godets (metal rolls with heating or cooling capability)to orient the polymer or quench existing orientation.

Polypropylene fibers may be used for, among other things, strapping,netting (including fish nets), slit tape, rope, twine, bags, carpetbacking, foamed ribbon, upholstery, rugs, pond liners, awnings,swimming-pool covers, tarpaulins, lawn-furniture webbing, shades,bristles, sutures, cigarette filters, nonwoven fabrics, such as for teabags, bed sheets, bandages, diaper liners and the like, and for dollhair, apparel and the like.

The graft copolymer of the present invention may also be used to improvethe compatibility of polymers in blends where they would otherwise bepoorly compatible. The graft copolymer is incorporated into such blends,preferably at levels of from about 0.2 to about 10%, preferably fromabout 0.5 to about 5%, and more preferably from about 0.8 to about 2.5%,to achieve the desired improvement in compatibility. Higher levels ofthe graft copolymer may be used, but increases above the preferred levelgenerally shown only small improvements in compatibility.

As noted above, compatibility is not easily predicted. As a general rulenon-polar polymers are poorly compatible with more polar polymers, butpoorly compatible blends may also be found experimentally amongpolar-polar or non-polar-non-polar blends. Examples of the non-polarpolymers are olefinic polymers such as high- and low-densitypolyethylene and linear low-density polyethylene, polypropyleneincluding atactic polypropylene, poly-1-butene, poly-iso-butylene,ethylene-propylene rubber, ethylene-acrylic acid copolymer,ethylene-propylene-diene terpolymer rubber, ethylene-vinyl acetatecopolymer, poly (ethylene-propylene), polymethylpentenes, and ionomerssuch as polymers of ethylene with metal-salt-neutralized acrylic acid.

Relatively more polar polymers, called polar polymers for the purposesof this disclosure, include acrylonitrile-butadiene-styrene polymer,acetal polymers, polyarylates, acrylic-styrene copolymers,acrylonitrile-styrene-acrylic polymers, acrylonitrile-styrene polymersmodified with ethylene-propylene rubber, cellulosics,polyester-polyether block copolymers, polyesters such as polybutyleneterephthalate and polyethylene terephthalate, and includingliquid-crystal polyesters, polyetheramides, polyetheretherketones,polyetherimides, polyethersulfones, ethylene-vinyl alcohol copolymers,polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidenechloride and fluoride, styrene polymers such as polystyrene, high-impactpolystyrene, styrene-acrylonitrile copolymers, styrene-butadienecompolymers, styrene-maleic anhydride copolymers, alkyl-substitutedstyrenes copolymerized with styrene alone or with the additionalmonomers listed for styrene, polyphenylene ether, polyphenylene sulfide,polysulfone, polyurethane, polyamides, i.e., nylons such as nylon 6,nylon 6.6, nylon 6.9, nylon 6.10, nylon 6.12, nylon 11, nylon 12,amorphous nylons, polyamideimide, polycaprolactone, polyglutarimide,poly(methyl methacrylate), other C₁ to C₈ poly(alkyl(meth)acrylates) andpolycarbonates. The acrylic polymers referred to above are polymerscontaining at least 50 weight percent, and preferably at least 80 weightpercent, of mers of acrylic acid and/or methacrylic acid (referred tocollectively as (meth)acrylic acid) or their esters, preferably theiralkyl esters and more preferably their alkyl esters in which the alkylgroup contains from one to eight, preferably one to four, carbon atoms.The remaining mers are those from one more monomers copolymerizable withthe (meth)acrylic acid or ester by free-radical polymerization,preferably vinylaromatic monomers, vinyl esters or vinyl nitriles, andmore preferably mers of styrene or acrylonitrile.

In the examples which follow, polymer concentrates and polymer blendswere tested using standard procedures which are summarized below.

Unreacted monomer in the reaction mixture prior to solvent removal orsubsequent to extruder devolatilization was determined using a gaschromatographic technique.

The collected volatiles were analyzed by gas chromatography on a 25meter CP wax 57 CB wall coated open tubular fused silica column at 40°C. A comparison of the major signals for the solvent with the MMA signalwas used to determine the amount of residual monomer in the reactor andtherefore give a measure of conversion immediately. A more accuratemeasure of conversion was obtained by a C,H,O analysis of the graftcopolymer. The carbon content was used to calculate EPDM orpolypropylene content by interpolating between the carbon content ofEPDM (85.49%) or polypropylene (85.87%) and acrylic polymer (60.6%).

The graft copolymers are analyzed by solvent extraction to remove theungrafted (meth)acrylic portion, whose molecular weight is thendetermined by gel permeation chromatographic technique. A technique forseparating the graft copolymer from ungrafted polyolefin is notavailable. For concentrates, 0.8-1.3 g of polymer was placed in acentrifuge tube with 17 cm³ of xylene. The tube was shaken overnight.Then the tube was placed in an oil bath set at 138° C. The tubes wereperiodically taken from the bath and shaken until all polymer haddissolved. The fact that all dissolved indicates that no crosslinkingoccurred. The tubes were cooled during which time the polypropylenecontaining substances precipitate. Then the tubes were centrifuged at15,000 rpm for 2 hours and the xylene solution was removed with care notto remove any floats. The molecular weight of the acrylic polymerextracted by the xylene was determined by gel permeation chromatography.The procedure was repeated on the resulting plug to extract additional(meth)acrylate. The value labelled % graft is the portion of the(meth)acrylic polymer formed which remains with the polyolefin plugafter repeated extraction. The composition is determined from the carbonanalysis of this plug.

The polypropylene concentrate and any additives were blended in the melton a 7.6 cm by 17.8 cm electric mill with a minimum gap of 3.8 mm set at190° C. Once the material had fluxed, it was mixed an additional 3minutes. Higher temperatures were used for higher viscosity materials(for example, mfr=0.5-2 material was done at 195°-210° C.). While stillhot, the material was either compression molded or cut into small chunks(about 1-2 cm in each dimension) for granulation (5 mm screen). It is ofinterest that the additives of the present invention contribute to easyrelease from hot metal surfaces, such as mill rolls, Haake Rheocordbowls, etc.

Milling of polyethylene was done in a similar manner except that theHDPE blends were milled at 200° C. and the LLDPE blends were milled at170° C.

A 2.5 cm Killion extruder was used for extrusion blending. A two stagescrew was used at 150 rpm, with all three zones set for 190° C. Theone-strand die was also set at the same temperature. A vacuum vent wasused. The strand was cooled in water and pelletized. The extrusion ratewas 4.5 kg per hour.

Melt blending in a Haake Rheocord (a batch melt mixer) was done on 50 gsamples at 190° C. or at 210° C. and 100 rpm in air. Mixing wascontinued for three minutes after peak torque was reached. Sample sizewas 50 grams.

The polyolefin blends were compression molded in an electrically heatedCarver press 15×15 cm or Farrel press 30.5×30.5 cm. The samples weremolded between aluminum plates with an appropriate spacer to provide therequired thickness 0.25-3.8 mm. In one method the hot melt was takendirectly from the mill roll and placed between two aluminum sheets. Thiswas then placed in the press set at 190° C. and pressed at high pressure(68-91 metric tonnes for the Farrel press and 6820 kg for the Carverpress). After three minutes the mold was placed in an unheated press athigh pressure for three minutes. In the other procedure, granulatedmaterial or pellets produced from an extrusion, Haake, or millingoperation were dried and then compression molded. The procedure used wasthe same as for molding a melt except that a 5 minute preheat was usedwhile maintaining a slight pressure on the press. This was followed bythe high pressure molding in the hot and cold presses. A hot press of190° C. was usually sufficient for mfr= 4 polypropylenes, but higherviscosity polypropylenes would split during sag testing unless highermolding temperatures were used (195°-210° C.).

Polyethylene was molded in a similar manner except that HDPE was moldedat 170° C. and LLDPE at 150° C.

Injection molding of polypropylene was performed on a Newbury injectionmolding machine in an ASTM family mold. Material to be molded was driedfor 16 hours at 60° C. The first barrel zone was set for 204° C., andthe other two barrel zones and the nozzle were set for 218° C. The ramtime was set for 3 seconds and the cycle of 15 seconds for injection and45 seconds overall was used. The injection pressure was 2100 kPa and theback pressure was 690 kPa. The screw speed was 100 rpm. Both moldplatens were set for 60° C.

The sag tests are performed on a compression molded sheet 10×10×0.15 cm.This sheet was clamped in a frame with a 7.6-cm-square opening. Therewere metal rulers attached to the front and back of the frame for use inmeasuring sag. The frame and sheet were placed in a hot, forced air oven(typically at 190° C.). The amount of sag of the center of the sheet wasthen recorded as a function of time. Typically, the sag was firstrecorded at 2.5 cm but for slow sagging materials sags as low as 16 mmwere recorded. Data was recorded up to 10.2 cm of sag or for 30 minutes,whichever occurred first.

The term "slope" refers to the slope of a plot of the natural logarithmof the sag in centimeters versus time, resulting in a straight line. Ahigh slope indicates that the material sags quickly while a low slopeindicates that it sags slowly. The advantage of comparing slopes in thismanner is that it eliminates any differences in oven cooling when thesample is introduced (due to differences in the time the oven is open,room temperatures, etc.).

Crude thermoforming was done in the laboratory to illustrate this meltstrength effect. A sheet of polypropylene or modified polypropylene washeated in a forced air oven at 190° C., removed from the oven, placedover a female mold, and subjected to vacuum.

The capillary flow data were measured on a Sieglaff McKelvey rheometer.The flows were recorded at ten shear rates (1 to 100-reciprocal seconds)at each temperature. The data was fit to the power law, i.e.,viscosity=k(temperature)×(shear rate)y, and the values at 1 and 1000reciprocal seconds were calculated from this best fit equation. Theparallel plate viscosity refers to measurements on the RheometricsDynamic Spectrometer, recorded at a strain of 5%.

Differential scanning calorimeter (DSC) measurements of melting andnucleation were performed on a duPont instrument. A value of 59 cal/gwas used for the heat of crystallization and per cent crystallinity wascorrected for the presence of the melt additive. The nucleationtemperature was measured in an experiment in which the polypropylene wasmelted at 200° C. for 2 minutes and then cooled at 10° C./min. Thetemperature at which peak crystallization occurred is called thenucleation temperature. The isothermal crystallization time was recordedby cooling the molten polypropylene quickly to 127° C. and the exothermrecorded with time.

The physical properties of the polypropylene homopolymer and "mediumimpact" copolymer are determined on extruded and injection moldedsamples, although similar results have been observed in milled andcompression molded samples. In certain examples below are describedspecialized equipment for preparing foamed sheet, rod or profile,extruded rod or tubing, fibers, cast film, monoaxially oriented andbiaxially oriented film, and injection blow-molded bottles or hollowcontainers.

The examples are intended to illustrate the present invention and not tolimit it except as it is limited by the claims. All percentages are byweight unless otherwise specified and all reagents are of goodcommercial quality unless otherwise specified.

EXAMPLE 1

This example illustrates preparation of a Graft Copolymer (GCP) ofPolypropylene (PP), Methyl Methacrylate (MMA) and Ethyl Acrylate (EA).

A polypropylene-acrylic graft copolymer is made by polymerizing a 5%ethyl acrylate (EA)- 95% methyl methacrylate (MMA) monomer mixture inthe presence of polypropylene (weight ratio ofpolypropylene:monomer=0.67:1). Radicals are generated fromditertiary-butyl peroxide (DTBPO) at the rate of 0.00010 moles per literper minute (radical flux). Monomer and initiator are fed over 60 minutesand the theoretical (100% conversion) solids at the end of the reactionis 55%.

A 6.6 liter reactor equipped with a double helical agitator (115 rpm)was charged with 1780 g of an inert hydrocarbon solvent mixture of2-methylalkanes having 6-12 C-atoms and 880 g polypropylene (mfr=4) andheated to 175° C. After 2 hours the temperature was decreased to 155° C.and the batch was stirred for 1 additional hour. Over a two minuteperiod two solutions were added. The first consisted of 1.04 g ofdi-t-butyl peroxide in 21 g of the hydrocarbon solvent. The secondconsisted of 0.06 g of di-t-butyl peroxide in 2.1 g of ethyl acrylateand 42 g of methyl methacrylate. For the next 58 minutes at the samefeed rate a feed of 1.87 g of di-t-butyl peroxide and 62 g of ethylacrylate in 1215 g of methyl methacrylate was added at the same feedrate as the second feed. This feed schedule results in a radical flux of0.00010 during the feed time. After the feed was complete the reactionwas held at 155° C. for an additional 15 minutes. Then it wasdevolatilized by passing through a 30-mm Werner-Pfleiderer extruder withtwo vacuum vents at 200°-250° C. The concentrate product (concentrate)is a mixture wherein the elemental analysis showed that the compositionis 56% (meth)acrylate. Extractive results showed 15.9% of thepolymerized (meth)acrylic monomers were grafted, and the M_(w) of the(meth)acrylic polymer was 91,300. The concentrate may be blended withother thermoplastic polymers such as polypropylene.

The following Table shows the efficiency of the above concentrateblended at different levels in improving sag resistance of apolypropylene homopolymer having a melt flow rate(mrf=4) of four.

                  TABLE I                                                         ______________________________________                                        Wt. % of   sag          sample   sag at                                       concentrate                                                                              slope,       thickness                                                                              17 min                                       in blend   min.sup.-1   (mm)     (cm)                                         ______________________________________                                        0          0.18         1.75     2.29                                         1.5        0.12         1.45     6.10                                         2.5        0.12         1.70     4.57                                         3.3        0.06         1.78     3.05                                         5.0        0.045        1.73     1.27                                         7.5        0.030        1.75     1.02                                         ______________________________________                                    

EXAMPLES 2-51

A polypropylene-acrylic graft copolymer is made by polymerizing a 5%ethyl acrylate (EA)-95% methyl methacrylate (MMA) monomer mixture in thepresence of polypropylene (weight ratio ofpolypropylene:monomer=0.67:1). Radicals were generated fromdi-tertiary-butyl peroxide (DTBPO) at the rate of 0.00010 moles perliter per minute (radical flux). Monomer and initiator were fed over 60minutes and the theoretical (100% conversion) solids at the end of thereaction was 52.5%.

A 6.6 liter reactor equipped with a pitched-blade turbine agitator (375rpm) was charged with 1880 g hydrocarbon solvent and 840 g polypropyleneand heated to 155° C. The mixture was stirred for 3 hours. Over a twominute period two solutions were added. The first consisted of 1.06 g ofdi-t-butyl peroxide in 21 g of hydrocarbon solvent, as in Example 1. Thesecond consisted of 0.06 g of di-t-butyl peroxide in 2.1 g of ethylacrylate and 40 g of methyl methacrylate. For the next 58 minutes a feedof 1.87 g of di-t-butyl peroxide and 61 g of ethyl acrylate in 1157 g ofmethyl methacrylate was added at the same feed rate as the second feed.This feed schedule should produce a radical flux of 0.00010 during thefeed time. After the feed was complete, the reaction was held at 170° C.for an additional 15 minutes. Then it was devolatilized by passingthrough a 30-mm Werner-Pfleiderer extruder with vacuum vents at200°-250° C. The concentrate showed that the composition is 51%acrylate.

Additional polypropylene-acrylic graft copolymers (Examples 2-51) wereprepared by the procedure of this Example and evaluated as 3.5% blendsin polypropylene (mfr=4) as melt strength additives. The following Tableillustrates the polymerization conditions for the concentrate and thepercent acrylic polymer present in the concentrate with the sagresistance of the blend with the polypropylene.

In the following Table II, DTBPO is di(t-butyl)peroxide, TBPB is t-butylperbenzoate, and DDBH is 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

                                      TABLE II                                    __________________________________________________________________________       sag slope                                                                          % acrylic  solids                                                                            polymer                                                                            feed time                                                                          radical                                                                           % EA                                     Ex.                                                                              min.sup.-1                                                                         in conc                                                                             initiator                                                                          %   temp. °C.                                                                   min  flux                                                                              in MMA                                   __________________________________________________________________________    Con*                                                                             0.15-0.18                                                                          --    --   --  --   --   --  --                                        1 0.03-0.05                                                                          56    DTBPO                                                                              55  155   60  0.00010                                                                           5                                         2 0.06 51    DTBPO                                                                                52.5                                                                            155   60  0.00010                                                                           5                                         3 0.06 52    DTBPO                                                                              55  155   60  0.00010                                                                           5                                         4  0.045                                                                             55    DTBPO                                                                              55  150   60  0.00010                                                                           5                                         5 0.08 57    DTBPO                                                                              55  145   60  0.00010                                                                           5                                         6 0.05 57    DTBPO                                                                              57  150   60  0.00010                                                                           5                                         7 0.10 49    DTBPO                                                                              55  150   60  0.00007                                                                           5                                         8 0.06 53    DTBPO                                                                              55  150   60  0.00015                                                                           5                                         9 0.06 55    DTBPO                                                                              55  150   60  0.00010                                                                           10                                       10 0.11 53    DTBPO                                                                              55  150   60  0.00010                                                                           0                                        11  0.056                                                                             48    DTBPO                                                                              55  155   60  0.00010                                                                           10                                       12 0.07 51    DTBPO                                                                              50  150    60 0.00010                                                                           5                                        13 0.11 58    DTBPO                                                                              55  145  120  0.00007                                                                           5                                        14 0.10 57    TBPB 55  145  120  0.00007                                                                           5                                        15 0.09 56    TBPB 55  150  120  0.00010                                                                           5                                        16 0.12 54    TBPB 55  150  120  0.00007                                                                           5                                        17 0.13 55    TBPB 55  150  120  0.00015                                                                           5                                        18 0.06 55    DTBPO                                                                              55  150  120  0.00007                                                                           5                                        19 0.06 49    TBPB 55  150   60  0.00010                                                                           5                                        20 0.10 51    TBPB 55  150  120  0.00010                                                                           5                                        21 0.14 57    TBPB 56  150  120  0.00010                                                                           5                                        22 0.13 51    TBPB 55  150   60  0.00010                                                                           5                                        23 0.15 55    TBPB 55  150  120  0.00010                                                                           0                                        24 0.15 56    DDBH 55  150  120  0.00010                                                                           5                                        25 0.14 57    TBPB 55  150  120  0.00015                                                                           5                                        26 0.09 51    TBPB 55  150   60  0.00010                                                                           5                                        27 0.15 54    DDBH 55  150  120  0.00010                                                                           0                                        28 0.11 51    DDBH 55  155  120  0.00010                                                                           5                                        29 0.10 53    DTBPO                                                                              50  150  120  0.00007                                                                           5                                        30 0.10 54    DTBPO                                                                              50  150  120  0.00005                                                                           5                                        31 0.15 53    DTBPO                                                                              50  150  120  0.00005                                                                           5                                        32 0.10 51    DTBPO                                                                              55  150  120  0.00007                                                                           5                                        33 0.12 55    TBPB 55  150  120  0.00007                                                                           5                                        34 0.18 55    DDBH 55  150  120  0.00007                                                                           5                                        35 0.07 53    DTBPO                                                                              55  150  120  0.00005                                                                           5                                        36 0.09 51    DTBPO                                                                              55  150  120  0.00010                                                                           5                                        37 0.14 51    TBPB 55  150  120  0.00005                                                                           5                                        38 0.10 37    DTBPO                                                                              55  155   60  0.00010                                                                           5                                        39 0.11 43    DTBPO                                                                              55  155  120  0.00007                                                                           5                                        40 0.08 48    DTBPO                                                                              55  155  120  0.00005                                                                           5                                        41 0.10 47    DTBPO                                                                              55  155  120  0.00007                                                                           5                                        42 0.07 48    DTBPO                                                                              55  155   60  0.00010                                                                           5                                        43 0.10 43    DTBPO                                                                              55  155  120  0.00005                                                                           5                                        44 0.10 50    DTBPO                                                                              55  155  120  0.00007                                                                           5                                        45 0.10 54    DTBPO                                                                              55  150  120  0.00010                                                                           5                                        46 0.10 54    DTBPO                                                                              55  150  120  0.00007                                                                           5                                        47 0.07 54    DTBPO                                                                              55  150  120  0.00005                                                                           5                                        48 0.08 56    DTBPO                                                                              55  150  120  0.00007                                                                           5                                        49 0.08 55    DTBPO                                                                              55  145  120  0.00007                                                                           5                                        50 0.09 56    DTBPO                                                                              55  145  120  0.00005                                                                           5                                        51 0.08 55    DTBPO                                                                              55  145  120  0.00010                                                                           5                                        __________________________________________________________________________     *Control = PP with no concentrate                                        

The calculated percent of grafted acrylic polymer and the molecularweight (M_(w)) of ungrafted acrylic material are tabulated below inTable III on certain samples where the ungrafted acrylic polymer wasseparated from the concentrate by extraction.

                  TABLE III                                                       ______________________________________                                                     % Acrylic Polymer                                                Example      Grafted to PP M.sub.w                                            ______________________________________                                         2           12.3          107,000                                            10           10.6          119,000                                            11           29.8          71,800                                             45           14.8          43,000                                             46           10.7          62,000                                             47           21.7          87,300                                             ______________________________________                                         Note:                                                                         (M.sub.w = weight average molecular weight)                              

EXAMPLE 52-54

This example shows a larger scale preparation of a polypropyleneacrylicgraft copolymer made by polymerizing a 5% ethyl acrylate (EA)-95% methylmethacrylate (MMA) monomer mixture in the presence of polypropylene(weight ratio of polypropylene:monomer=0.67:1). Radicals were generatedfrom di-tertiary-butyl peroxide (DTBPO) at the rate of 0.000065 molesper liter per minute (radical flux). Monomer and initiator were fed over122 minutes and the theoretical (100% conversion) solids at the end ofthe reaction was 47%.

A 380 liter reactor equipped with a back-slope turbine agitator wascharged with 102.3 kg of the hydrocarbon solvent and 36.4 kg of mfr=4polypropylene homopolymer and heated to 150° C. over 4 hours. Twosolutions were added over a twenty minute period. The first consisted of82 g of di-tertiary-butyl peroxide in 826 g of the hydrocarbon solvent.The second consisted of 454 g of EA and 8.6 kg of MMA. Addition of thefirst solution was then continued at a lower rate to feed an additional82 g of di-tertiary-butyl peroxide and 826 g of the hydrocarbon solventover 90 minutes. At the same time the monomer addition of 2.3 kg of EAand 47.5 kg of MMA was continued over 102 minutes (ending 12 minutesafter the initiator feed had finished). The reaction was held at 150° C.for an additional 15 minutes. Then an additional 23 kg of hydrocarbonsolvent was pumped in over 30 minutes. The reaction mixture was thendevolatilized by passing through a 20-mm Welding Engineers twin-screwextruder at 200 rpm and 200°-250° C. over 14 hours. This concentrate isEx. 52. Similar preparations labelled 53 and 54 were synthesized withchanges in feed time and radical flux as indicated. The following TableIV shows the improvement in sag resistance when concentrates of Example52, 53 and 54 are blended with polypropylene of mfr=4:

                                      TABLE IV                                    __________________________________________________________________________       %       Weight                                                                Conc                                                                              Sag Fraction                                                              in  Slope                                                                             Acrylic                                                                            Initi-   Polymer                                                                            Feed                                                                             Rad.                                         Ex.                                                                              Blend                                                                             min.sup.-1                                                                        in conc.                                                                           ator Solids                                                                            temp Time                                                                             Flux                                         __________________________________________________________________________    Con.                                                                             none                                                                              0.19                                                                              --                                                                 52 2.5 0.11                                                                              0.6  DTBPO                                                                              47  150  122                                                                               0.000065                                       3.5 0.10                                                                   53 3.5 0.11                                                                              0.6  DTBPO                                                                              45  150  90 0.00007                                         5.0 0.10                                                                   54 3.5 0.15                                                                              0.6  DTBPO                                                                              49  150  78 0.00008                                         5.0 0.09                                                                   __________________________________________________________________________

EXAMPLE 55

This example and Table V demonstrate the unexpected advantage of theconcentrate of Example 4 in the improvement of sag resistance for bothhigh density polyethylene (HDPE) and linear low density polyethylene(LLDPE). Data for HDPE are for polymers of two different mfr values (4and 8) and are obtained at 150° C. The LLDPE values are on a singleresin having a density of 0.917 g/cc, but at two different temperatures.Comparison molded polyethylene samples prepared for this test had asignificant increase in gloss over the unmodified control.

                  TABLE V                                                         ______________________________________                                                 Wt % Add-        Time to Sag. Minutes                                Polyethylene                                                                             itive     Temp °C.                                                                        762 mm 50.8 mm                                  ______________________________________                                        HDPE, mfr = 8                                                                            0         150      8.7    9.3                                                 2                  10.2   11.9                                                3.5                15.8   30.0                                                5                  31.4   --                                       HDPE, mfr = 4                                                                            0         150      8.0    9.0                                                 3.5                10.5   12.0                                                5                  26.0   --                                       LLDPE, mfr = 2                                                                           0         170      5.3    6.0                                                 5                  17.7   21.4                                     LLDPE, mfr = 2                                                                           0         180      4.6    5.2                                                 5                  8.5    10.0                                     ______________________________________                                    

EXAMPLE 56

A polyethylene-acrylic graft copolymer concentrate was synthesized in amanner similar to that previously described for polypropylene-acrylicgraft copolymers. The polyethylene-acrylic graft copolymer concentratewas made by polymerizing a 100% methyl methacrylate (MMA) monomermixture in the presence of polyethylene (weight ratio ofpolyethylene:monomer=0.5:1). Radicals were generated fromdi-tertiary-butyl peroxide (DTBPO) at the rate of 0.00010 moles perliter per minute (radical flux). Monomer and initiator were fed over 60minutes and the theoretical (100% conversion) solids at the end of thereaction was 55%.

A 6.6 liter reactor equipped with a double helical agitator (115 rpm)was charged with 1760 g hydrocarbon solvent and 725 g polyethylene(mfr=4, density=0.95) and heated to 150° C. The mixture was stirred for3 hours. Over a two minute period two solutions were added. The firstconsisted of 1.63 g of di-t-butyl peroxide in 48 g of methylmethacrylate. For the next 58 minutes a feed of 1.73 g of di-t-butylperoxide in 1401 g of methyl methacrylate was added at the same feedrate as the second feed. This feed schedule should produce a radicalflux of 0.00010 during the feed time. After the feed was complete thereaction was held at 150° C. for an additional 15 minutes. Then it wasdevolatilized by passing through a 30-mm Werner-Pfleiderer extruder withvacuum vents at 200°-250° C. The elemental analysis showed that theconcentrate contained 64% (meth)acrylate.

EXAMPLE 57

This example shows that both polyethylene-acrylic graft polymer andpolypropylene-acrylic graft polymer concentrate were effective atreducing the sag of HDPE. The blend of concentrate with HDPE mfr=4 anddensity=0.95 was milled at 220° C. and the hot material from the millwas molded at 210° C. Sags were measured by the same procedure used forpolypropylene sheet except that an oven temperature of 150° C. was used.

                  TABLE VI                                                        ______________________________________                                                                             76.2 mm                                  Concentrate       Sag Slope 25.4 mm Sag                                                                            Sag                                      of Example                                                                             % Conc.  min.sup.-1                                                                              (min)    (min)                                    ______________________________________                                        Control  none     0.57      7.4      9.4                                      56       5%       0.27      9.0      13.0                                     56       10%      0.11      10.0     19.8                                     4        5%       <0.015    15.0     30 min to                                                                     31.7 mm                                  ______________________________________                                    

EXAMPLE 58

This example shows that the polyethylene and polypropylene graftcopolymer concentrates are effective in improving sag resistance of HDPEwhile ungrafted acrylic polymer of similar M_(w) is not. Addition of asmuch as 5% of a commercial acrylic molding powder poly(methylmethacrylate), M_(w) 105,000, designated "A") showed no decrease in sagrate, while 3% poly(methyl methacrylate) present as the graft copolymerconcentrate resulted in large reductions of sag rate.

The specific concentrate used in part of this study was synthesized inthe following manner. The polypropylene-acrylic graft copolymer was madeby polymerizing a 5% ethyl acrylate (EA)-95% methyl methacrylate (MMA)monomer mixture in the presence of polypropylene of mfr=0.4 (weightratio of polypropylene:monomer=0.67:1). Radicals were generated fromdi-tertiary-butyl peroxide (DTBPO) at the rate of 0.00007 moles perliter per minute (radical flux). Monomer and initiator were fed over 120minutes and the theoretical (100% conversion) solids at the end of thereaction was 55%.

A 6.6 liter reactor equipped with a pitched-blade turbine agitator (375rpm) was charged with 1780 g of the hydrocarbon solvent and 880 gpolypropylene (mfr=0.4) and heated to 160° C. The mixture was stirredfor 2 hours and then the temperature was decreased to 150° C. for onehour. Over a two minute period two solutions were added. The firstconsisted of 1.22 g of di-t-butyl peroxide in 20 g of the hydrocarbonsolvent. The second consisted of 0.0002 mg of monomethyl ether ofhydroquinone (MEHQ) and 0.05 g of di-t-butyl peroxide in 1.1 g of ethylacrylate and 21 g of methyl methacrylate. For the next 118 minutes afeed of 13 mg MEHQ and 2.70 g of di-t-butyl peroxide in 66 g of ethylacrylate and 1253 g of methyl methacrylate was added at the same feedrate as the second feed. This feed schedule should produce a radicalflux of 0.00007 during the feed time. After the feed was complete thereaction was held at 150° C. for an additional 15 minutes. Then it wasdevolatilized by passing through a 30 mm Werner-Pfleiderer extruder withtwo vacuum vents at 200°-250° C. The elemental analysis showed that theconcentrate contained 53% (meth)acrylate.

The blends of HDPE (mfr=7, density=0.95) and graft copolymer concentratewas milled at 200° C. and the hot materials were formed into sheets fromthe mill at 170° C. Sags were measured by the same procedure used forpolypropylene sheet except that an oven temperature of 150° C. was used.

                  TABLE VII                                                       ______________________________________                                               Concentrate                                                                              Sag Slope  25.4 mm 50.8 mm                                  Example                                                                              Level      min.sup.-1 sag (min)                                                                             sag (min)                                ______________________________________                                        Control                                                                              none       0.59       7.4     8.7                                      A      3.0%       0.58       7.1     8.3                                      A      5.0%       0.54       7.6     9.0                                      56     5.0%       0.27       --      10.3                                     4      2.0%       0.28       8.2     10.2                                     4      3.5%       0.056      9.4     15.8                                     4      5.0%       0.038      10.4    31.4                                     58     3.5%       0.37       7.4     9.2                                      58     5.0%       0.30       8.1     10.0                                     ______________________________________                                    

EXAMPLE 59

The concentrate of Example 4 was blended with LLDPE and the results ofevaluating the sag resistance improvements are shown below in TableVIII. The blend of modifier and LLDPE was milled at 170° C. and the hotmaterial from the mill was milled at 150° C. Sag resistance was measuredby the same procedure used for polypropylene sheet at the temperaturelisted.

"A" is an LLDPE having an mfr=2.3 and a density of 0.92, recommended forcasting and extruding applications.

"B" is an LLDPE having an mfr=1 and a density of 0.92, recommended forblow molding and extrusion applications.

                  TABLE VIII                                                      ______________________________________                                               Concen-  Sag     Sag Slope                                                                             25.4 mm                                                                              101.6 mm                               LLDPE  trate    Temp.   min.sup.-1                                                                            sag (min)                                                                            sag (min)                              ______________________________________                                        A      none     180° C.                                                                        0.58    3.4    5.6                                    A      5% Ex. 4 180° C.                                                                        0.24    5.2    10.6                                   A      none     170° C.                                                                        0.54    3.9    6.4                                    A      5% Ex. 4 170° C.                                                                        0.096   9.5    23.0                                   B      none     150° C.                                                                        --      7.8    15.6                                   B      5% Ex. 4 150° C.                                                                        --      33.7 min at 19 mm                             ______________________________________                                    

EXAMPLE 60

This example illustrates improved sag modification and increasednucleation temperature for polybutylene, when blended with theconcentrate. Polybutylene, injection grade, mfr=4, with and without 2.44wt. % of the concentrate of Example 20 were milled at 190° C. andpressed into plaques of about 1.7 mm thickness. Times were measured forvarious distances of sag at 145° C. DSC curves were used (heat/cooltime=20° C./min). A higher crystallization temperature relates toincreased speed of nucleation and solidification of the heated polymer.

                  TABLE IX                                                        ______________________________________                                        Weight                      DSC                                               Percent  Time to sag (min:sec)                                                                             Temperature, °C.                          Concentrate                                                                            25.4 mm  50.8 mm  101.6 mm                                                                             Melt Crystallize                            ______________________________________                                        Conrtol (0)                                                                            5:20      7:50    10:23  128  45                                     2.44 wt %                                                                              7:24     15:53    >30    129  55                                     ______________________________________                                    

EXAMPLE 61

This example describes the preparation of a concentrate ofpolypropylene-acrylic graft copolymer made by polymerizing 5% ethylacrylate (EA)-95% methyl methacrylate (MMA) monomer mixture in thepresence of an equal amount of polypropylene. Radicals were generatedfrom di-tertiary-butyl peroxide (DTBPO) at the rate of 0.00017 moles perliter per minute (radical flux). Monomer and initiator were fed over 30minutes and the theoretical (100% conversion) solids at the end of thereaction was 50%.

A 6.6 liter reactor equipped with a double helical agitator (115 rpm)was charged with 1980 g of the hydrocarbon solvent and heated to 170° C.1000 g of polypropylene (mfr=5) was fed to the reactor via a meltextruder set at 200° C. at a rate of about 10 g per minute. After 45minutes hold at 170° C. the addition of monomer and initiator solutionswas begun. Over a two minute period two solutions were added. The firstconsisted of 0.44 g of di-t-butyl peroxide in 21 g of the hydrocarbonsolvent. The second consisted of 0.11 g of di-t-butyl peroxide in 1.3 gof ethyl acrylate and 65 g of methyl methacrylate. For the next 28minutes a feed of 1.59 g of di-t-butyl peroxide and 19 g of ethylacrylate in 914 g of methyl methacrylate was added at the same feed rateas the second feed. This feed schedule should produce a radical flux of0.00017 during the feed. After the feed was complete the reaction washeld at 170° C. for an additional 15 minutes. Then it was devolatilizedby passing through a 30-mm Werner-Pfleiderer extruder with vacuum ventsat 200°-250° C. The elemental analysis (carbon content) showed that theconcentrate contained 35% (meth)acrylate.

A sheet of polypropylene (mfr=4) with and without the concentrate ofthis example was heated in a forced air oven to 190° C., removed fromthe oven and immediately placed over a female mold and subjected tovacuum. The top and bottom corner measurements were the average of the 8measurements in mm at the corner of each of the four side faces of thebox. The top and bottom center measurements were the average of the 4measurements in mm at the center of the edge of the 4 faces of the box.These measurements are summarized in Table X and demonstrate smallerwall thickness variations when the concentrate is present.

                  TABLE X                                                         ______________________________________                                        WALL THICKNESS VARIATION IN                                                   THERMOFORMED PARTS                                                                      Top      Top       Bottom  Bottom                                   Polypropylene                                                                           Center   Corner    Center  Corner                                   ______________________________________                                        unmodified                                                                              1.14 mm  0.88 mm   0.75 mm 0.025 mm                                 5% Ex. 61 0.97 mm  0.97 mm   0.35 mm  0.21 mm                                 ______________________________________                                    

EXAMPLE 62

This example demonstrated the unexpected higher nucleation temperatureand shorter time for crystallization imparted by addition of thepolymeric concentrate of Examples 1 and 52 to polypropylene of mfr=4.The nucleation temperature was measured while cooling at 10° C./min, themelting temperature was measured while heating at 20° C./min and thecrystallization time was measured isothermally at 127° C. or 130° C. Theextent of crystallization was reported for both cooling and meltingmeasurements. Comparison was made with ungrafted PMMA of similar M_(w).

                                      TABLE XI                                    __________________________________________________________________________    Temp. of crystallization (°C.)                                                         127 127 130 130 130 130  130                                  Percent Concentrate                                                                           0   5   0   1.1 2.2 3.9  7.8                                  Polymer Concentrate of Example                                                                --  52  --  52  52  PMMA PMMA                                 Crystallization Time, min.                                                                    16.3                                                                              3.6 24.5                                                                              3.7 3.0 8.1  10.6                                 Nucleation Temperature, °C.                                                            105 112 107 118 118 112  110                                  % Crystallinity 39  40  41  46  42  42   41                                   Melting Temperature, °C.                                                               165 166 169 170 168 170  168                                  % Crystallinity 41  44  44  44  46  46   44                                   __________________________________________________________________________

EXAMPLE 63

This example demonstrated the lower equilibrium torque and improvementin time to flux for blends of the concentrate of Example 1 withpolypropylene of mfr=4 using the Haake Rheocord. The test conditions aredescribed above. Peak torque at flux was also reduced.

                  TABLE XII                                                       ______________________________________                                        Wt. %                                                                         Concentrate in                                                                             Time to flux                                                                             Equilibrium Torque                                    Polypropylene                                                                              (seconds)  (meter-grams at 215°                           ______________________________________                                        0            109        695                                                   3            50         690                                                   5            50         670                                                   ______________________________________                                    

EXAMPLE 64

This example shows that a propylene-acrylic graft copolymer concentratemay be used to improve the sag resistance of an acrylic sheet. About 20parts of the graft polymer of Example 1 was milled with 100 parts of acommercial acrylic molding powder of M_(w) 105,000 and compressionmolded. Sag tests indicated that the sheet containing the concentratemay be heated to about 5°-10° C. higher before flow equivalent to thatof the unmodified sheet was observed.

EXAMPLES 65-66

Graft copolymer concentrates were prepared according to the processdescribed in Examples 52-54, using the conditions shown in Table XIII.

                  TABLE XIII                                                      ______________________________________                                        Concen-                                                                       trate  % Acryl-              Monomer Feed                                                                            Rad-                                   of Exam-                                                                             ic       Initi-         Temp, Time  ical                               ple    In Conc. ator     Solids                                                                              °C.                                                                          (min) Flux                               ______________________________________                                        A      55       DTBPO    50%   150   120   0.00010                            B      55       DTBPO    50%   150   120   0.00007                            ______________________________________                                    

Concentrates A and B were blended together at a weight ratio of 2.8:1 toform concentrate C. As indicated in Table XIV, concentrate C was blendedat the 4% level with polypropylene and the indicated amounts ofdi-t-dodecyl disulfide (DTDDS) and extruded. The sag results for theseblends are given in Table XIV below.

                  TABLE XIV                                                       ______________________________________                                        Example                                                                              % Concentrate                                                                              DTDDS     Sag Slope in min.sup.-1                         ______________________________________                                        65     4            none      0.07                                            66     4            0.03%     0.05                                            67     4            0.3%      0.03                                            ______________________________________                                    

Stabilizing the concentrate during processing, as by using the DTDDS, isseen to produce even more significant improvement in melt strength.

EXAMPLE 67

This example further demonstrates that the graft copolymer has littleeffect on the high-shear viscosity but a pronounced effect on low-shearviscosity in polypropylene.

The graft copolymer of Example 1 was admixed at the five weight-percentlevel with an injection-molding grade of propylene homopolymer, mfr=4,as in Example 63. Capillary and parallel-plate viscosities were measuredat various temperatures under conditions described above, under both lowand high shear conditions. The results shown in Table XV belowdemonstrate the increase in low shear viscosity, especially attemperatures below about 210° C., with essentially no effect onviscosity at high shear rate.

                  TABLE XV                                                        ______________________________________                                                         Conditions:                                                                   Low Shear High Shear                                                      Tem-  Amount of                                                               per-  Graft Polymer:                                             Test           ature   0%      5%    0%   5%                                  ______________________________________                                        Capillary Viscosity.sup.(a)                                                                  180° C.                                                                        9400    133000                                                                              1900 2000                                Capillary Viscosity.sup.(a)                                                                  190° C.                                                                        80000   110000                                                                              1900 1600                                Capillary Viscosity.sup.(a)                                                                  210° C.                                                                        57000    75000                                                                              1200 1100                                Parallel Plate Viscosity.sup.(b)                                                             190° C.                                                                        63000    99000                                                                              2100 2100                                Parallel Plate Viscosity.sup.(b)                                                             210° C.                                                                        54000    58000                                                                              1800 1800                                Parallel Plate Viscosity.sup.(b)                                                             230° C.                                                                        37000    39000                                                                              1500 1400                                ______________________________________                                         Shear Conditions:                                                             .sup.(a) Low Shear = 1.0 sec.sup.-1 ; high shear = 1000 sec.sup.-1            .sup.(b) Low Shear = 0.1 sec.sup.-1 ; high shear = 500 sec.sup.-1        

EXAMPLE 68

This example shows improved stabilization to weight loss on heating byuse of a disulfide or a substituted triazine stabilizer. Apolypropylene-acrylic graft copolymer similar to that of Example 4 wasblended with stabilizers on the mill roll. The graft copolymer (98grams) was fluxed on the mill at 195° C. The stabilizer (2 grams) wasadded and blended in for 2 minutes. The material was removed from themill, cut into chunks, and granulated. One or more of these stabilizedversions were then let down in a similar manner in additional graftcopolymer to produce graft copolymer stabilized at the 100-5000 ppmlevel. The results on the TGA of stabilization are shown in the table.Weight loss (%) is the temperature at which the particular percentweight loss is observed, utilizing a DuPont ThermoGravimetric Analyzerat a heating rate of 20° C. in nitrogen. Although none of thestabilizers were deleterious to stability, only those designated 2 and 7exhibited significant stability advantages.

The stabilizers studied were:

1. DLTDP (dilauryl thiodipropionate);

2. TNPP (trisnonylphenyl phosphite);

3. Irganox 1010(tetrakis(methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate))methane);

4. DTDDS (di-t-dodecyldisulfide);

5. Irgafos 168 (tris-(2,4-di-t-butylphenyl)phosphite);

6. Weston 618 (di-stearyl pentaerythritol diphosphite);

7. Cyanox 1790(tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-s-triazine-2,4,6-(1H,3H,5H)-trione;

8. Irganox 1076 (octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate);

9. Topanol CA (3:1 condensate of 3-methyl-6-t-butylphenol withcrotonaldehyde.

                                      TABLE XVI                                   __________________________________________________________________________                               WEIGHT LOSS                                                                   TEMPERATURE                                        STABILIZER (PPM)           (DEGREES C.)                                       1  2  3  4  5  6  7  8  9  1%   10%                                           __________________________________________________________________________                               279  325                                           600                        274  318                                           2000                       281  328                                              600                     280  327                                              2000                    271  317                                                 2000                 275  320                                                    300               286  345                                                    1000              297  368                                                                      272  317                                           600   2000                 279  323                                           2000  2000                 278  322                                              600                                                                              2000                 280  323                                              2000                                                                             2000                 278  321                                                 2000                                                                             300               291  358                                           600   2000                                                                             600               280  324                                                                      273  319                                                       600            273  318                                                       2000           271  318                                                          600         272  319                                                          2000        272  319                                                       600   2000     273  320                                                       2000  2000     274  321                                                          600                                                                              2000     285  328                                                          2000                                                                             2000     279  322                                           600               2000     296  333                                           2000              2000     298  338                                              600            2000     286  328                                              2000           2000     285  325                                                             2000     285  325                                                 2000  600            278  321                                                 2000  2000           277  321                                                 2000     600         276  321                                                 2000     2000        277  319                                                             1000     280  319                                                             2000     285  323                                                             4000     291  329                                                    100      1000     285  329                                                    300      1000     289  331                                                    100      2000     289  327                                                    300      2000     292  335                                           600               2000     282  325                                           1000              2000     288  325                                           1000              4000     291  331                                           2000              4000     291  331                                                                2000  278  318                                                                   2000                                                                             278  322                                           1000                 2000  277  316                                                    300         2000  285  326                                           1000                    2000                                                                             280  321                                                    600            2000                                                                             286  327                                           __________________________________________________________________________

EXAMPLE 69

This example illustrates the preparation of a larger amount of graftcopolymer to be used in many of the following studies. The process andcomposition of Example 52 was followed with some variations. Severalpreparations were combined. In all but the last of these preparations,radicals are generated at the rate of 0.000070 moles per liter perminute (radical flux). Monomer and initiator are fed over 120 minutesand the theoretical (100%) conversion) solids at the end of the reactionis 50%.

A 380-liter reactor equipped with a pitched-blade turbine agitator wascharged with 86.4 kg of the hydrocarbon solvent and 34.5 kg ofpolypropylene homopolymer, mfr=4. After deoxygenating (applying vacuumto degas, followed by pressurizing with nitrogen to atmosphericpressure) through three cycles, it was pressurized to 103 kPa withnitrogen and heated to 150° C. over 2 hours. A pressure of 241 kPa wasmaintained while the batch was held at 150° C. for 3 hours. Twosolutions were added over a fifteen minute period. The first consistedof 59 g of DTBPO in 841 g of the hydrocarbon solvent. The secondconsisted of 0.32 kg of ethyl acrylate and 6.14 kg of methylmethacrylate. Addition of the first solution was then continued at alower rate to feed an additional 103 g of DTBPO and 1479 g of thehydrocarbon solvent over 105 minutes. At the same time the monomeraddition of 2.26 kg of ethyl acrylate and 43.0 kg of methyl methacrylatewas continued over 105 minutes. Reaction exotherm increased thetemperature to about 160° C. After the feed was complete, 5 kg of thehydrocarbon solvent was fed into the reaction mixture.

The reaction mixture was held in the reaction kettle for an additional30 minutes. It was then transferred to a second kettle which was alsounder pressure at 150° C. During the transfer a solution of 80 g ofdi-tertiary dodecyl disulfide in 320 g of the hydrocarbon solvent wasadded to the second kettle. Also during this transfer three 4.53 kgportions of the hydrocarbon solvent were fed into the reaction kettle.Material in this second kettle was fed to a 20.3-mm Welding Engineerstwin-screw extruder where devolatilization occured.

During the devolatilization the next batch was prepared in the reactionkettle. It was transferred to the extruder feed kettle while extrusioncontinued. In this manner several batches were made in a "semi-batch"manner, that is, batchwise in the reactor with continuous feed to theextruder.

In the final preparation of the blend, radical flux was 0.000050 (42 gDTBPO+858 g of the hydrocarbon solvent in the first feed, 73 gDTBPO+1502 g of the hydrocarbon solvent in the second feed).

The final blend, designated Example 69, was prepared by blending pelletsfrom 13 batches prepared as described and one batch of the finalvariant. All samples from individual batches gave acceptable sagresistance when tested in polypropylene.

EXAMPLE 70

The following example illustrates that improved stability can beimparted to the graft copolymers of the present invention bycopolymerization of an alkylthioalkyl monomer, specificallyethylthioethyl methacrylate.

The stability of graft copolymers prepared with alternate monomercompositions was also evaluated. All were prepared according to theprocedure for Example 4, except that the monomer composition varied andthe product was isolated by evaporating solvent instead of bydevolatilizing in an extruder. The monomer compositions and the TGAresults are summarized in the table below. The abbreviation EA indicatesethyl acrylate; MMA=methyl methacrylate; ETEMA=ethylthioethylmethacrylate and MA=methyl acrylate. Weight loss (%) is the temperatureat which the particular percent weight loss is observed, utilizing aDuPont ThermoGravimetric Analyzer at a heating rate of 20° C. innitrogen.

                  TABLE XVII                                                      ______________________________________                                                      Temperature at Which Noted                                                    Percent Weight Loss Occurs                                      Grafted Acrylic                                                                              by TGA Analysis (°C.)                                   Polymer       1%       2%      5%     10%                                     ______________________________________                                        95% MMA, 5% EA                                                                              221      274     307    333                                     95% MMA, 5% EA +                                                                            260      289     314    346                                     0.05% ETEMA                                                                   95% MMA, 5% EA +                                                                            281      305     335    360                                     0.25% ETEMA                                                                   95% MMA, 5% MA                                                                              254      290     317    325                                     ______________________________________                                    

EXAMPLE 71

This example illustrates that an alternative method reported for thepreparation of methacrylic ester//polyolefin graft copolymers does notproduce a polymer useful in improving resistance to sagging ofpolypropylene. Example 2 of U.S. Pat. No. 2,987,501 was repeated,wherein linear low-density polyethylene homopolymer (mfr=2.3) wasimmersed in fuming nitric acid for 30 minutes at 70° C., removed, washedwith water, and dried. The treated polyethylene was then suspended overrefluxing methyl methacrylate for 4 hours. The polymer was extractedwith methyl ethyl ketone, as taught in the reference, to removeungrafted poly(methyl methacrylate). The molecular weight of theungrafted polymer was determined by gel permeation chromatography to beMw=430,000, Mn 170,000.

                  TABLE XVIII                                                     ______________________________________                                        Weight of                                                                              Weight before                                                                             Weight after                                                                              Weight                                       polyethylene,                                                                          reaction (after                                                                           reaction and                                                                              of polymer                                   g.       nitration), g.                                                                            extraction, g.                                                                            extracted, g.                                ______________________________________                                        3.397    3.48        5.964       4.40                                         ______________________________________                                    

Thus, the graft copolymer formed was 43% PMMA and 57% PE. The totalsample prior to extraction was 67% PMMA, 33% PE, and the efficiency ofgrafting of the PMMA was 63.1%.

The resultant graft polymer, from which the ungrafted polymer had notbeen removed, was blended at the 4% level into the polypropylene resinof mfr=4 used as a standard for testing sag resistance. The graftcopolymer of this example did not disperse well, and visible, large,undispersed fragments were seen. The sag value (0.31) was worse than forthe unmodified resin (0.18) or for resin modified with an equivalentamount of the graft copolymer of Example 69 (0.02).

The graft copolymer of this example was also milled into linearlow-density polyethylene (mfr 2.3) in the manner taught in Example 59.Poor dispersion in polyethylene was also noted, with large chunks of theundispersed modifier visible. Sag resistance was determined at 150° C.as in Example 59; sag for the unmodified control (by the sag slope test)was 0.39, and for the graft copolymer of this example, 0.23. Bycomparison, sag when using the graft copolymer of Example 4 would beexpected to be well below 0.10.

EXAMPLES 72-77

This example illustrates preparation of blends of graft copolymer withpolypropylene resins to form pellets useful for further processing intoextruded or molded articles.

The graft copolymer of Example 69, not separated from any ungraftedpolypropylene or acrylic polymer, was used as 3.2-mm-long pellets cutfrom an extruded strand.

The polypropylene resins used were Aristech T1-4020F (Aristech ChemicalCorporation, Pittsburgh, Pa.), Himont 6523 (Himont Corporation,Wilmington, Del., and Rexene 14S4A (Rexene Corporation, Dallas, Tex.).Characteristics are shown in Table XIII; the term "copolymer" in thetable means a copolymer with ethylene.

The graft copolymer was blended at 5% with the polypropylene resins bytumbling. The blend was then extruded into strands through an Egan60-mm, twin-screw extruder equipped with screws of 32:1 length/diameterratio; the strands were cooled and chopped into pellets. Various feedrates and screw speeds were utilized. Conditions for the unmodified andmodified resins used to obtain large-scale samples are summarized inTable XIV. Sag tests as described in Example 1 were conducted on severalother samples of modified resin processed under varying conditions, andthe results were comparable to those reported below in Table XIX.

                  TABLE XIX                                                       ______________________________________                                        Blends of Polypropylene With Methyl Methacrylate                              Graft Copolymer and Controls                                                  Ex. 69                                                                        Graft,     Polypropylene Matrix Resin                                         Example                                                                              phr     Name       MFR   Composition                                                                            Sag                                  ______________________________________                                        72     --      Aristech   2     copolymer                                                                              0.23                                                TI-4020F                                                       73     5                                 0.02                                 74     --      Himont 6523                                                                              4     homopolymer                                                                            0.36                                 75     5                                  0.11*                               76     --      Rexene     4     copolymer                                                                              0.35                                                14S4A                                                          77     5                                 0.14                                 ______________________________________                                         *Sample tore on testing; other blends processed at slightly different         conditions gave sags of 0.06 to 0.09.                                    

                  TABLE XX                                                        ______________________________________                                        Processing Conditions for Pre-Blends of TABLE XIX                             Example:      72     73     74   75   76   77                                 Modifier:     --     5%     --   5%   --   5%                                 ______________________________________                                        Feed Rate, kg/hr (Set)                                                                      90.7   181.4  90.7 181.4                                                                              181.4                                                                              181.4                              Feed Rate (actual)                                                                          90.2   185    89.8 181.4                                                                              178.7                                                                              182.3                              Screw Speeds  101    200    100  200  200                                     200                                                                           Drive Amps    103    121    97   111  112  112                                Kg-m/s.sup.1  1258   3033   1184 2811 2811 2811                               Head Pressure (kPa)                                                                         2137   2758   1448 2068 2275 2206                               Barrel Temps. (°C.)                                                    Zone 1        163    163    163  163  163  163                                Zones 2-8     204    204    204  204  204  204                                Die           204    204    204  204  204  204                                Melt Temp. °C.                                                                       213    222    208  216  217  217                                ______________________________________                                         .sup.1 Power applied to extruder screw.                                  

EXAMPLES 78-83

This example illustrates preparations of blends of graft copolymer withother polypropylene resins on different compounding equipment to formpellets useful for further processing into film or profile. The Amoco6214 is a film grade polypropylene resin containing a clarifier. TheEastman 4E11 is an impact-extrusion grade, propylene-ethylene-copolymerresin used in profile extrusion. In the present case, both 1% and 5% byweight of the graft copolymer described in Example 69 were used to formthe blends.

The two polymers were tumble blended, and the mixtures fed to an 83 mmWerner-Pfleiderer co-rotating, intermeshing, twin-screw extruder of 24/1I/d ratio. The pellets were continuously fed to the extruder by means ofan Acrison "loss-in-weight feeder", melted and mixed in the extruder,extruded through a 33-strand die, cooled in a water trough, dried,pelletized, and packaged. The machine conditions for the individualbatches are as follows:

                  TABLE XXI                                                       ______________________________________                                        Compositions of Blends and Matrix Polymers                                    Example  % Modifier    Matrix Polymer                                         ______________________________________                                        78       --            Eastman 4E11 Copolymer                                 79       1                                                                    80       5                                                                    81       --            Amoco 6214 Homopolymer                                 82       1                                                                    83       5                                                                    ______________________________________                                    

                  TABLE XXII                                                      ______________________________________                                        Preparative Conditions for Various Blends of TABLE XXI                        Temperature, °C.                                                       Zone     set point/actual                                                                          Conditions                                               ______________________________________                                        Ex. 79                                                                              Z-1    229/229     RPM-      125                                              Z-2    235/216     TORQUE-   73-75%                                           Z-3    249/227     FEED SET- 65                                               Z-4    213/302     VACUUM-   380 mm Hg                                        Z-5    235/221     MELT TEMP.-                                                                             227° C.                                                                (STRANDS)                                        Z-6    227/227     RATE-     150 kg/hr                                        (DIE)                                                                         Z-7    238/241                                                                (DIE)                                                                   Ex. 80                                                                              Z-1    229/229     RPM-      125                                              Z-2    235/216     TORQUE-   73-75%                                           Z-3    249/235     FEED SET- 65                                               Z-4    213/302     VACUUM-   355-380 mm Hg                                    Z-5    235/232     MELT TEMP.-                                                                             205-207° C.                               Z-6    241/241     RATE-     218 kg/hr                                        Z-7    238/238                                                          Ex. 82                                                                              Z-1    288/288     RPM-      90                                               Z-2    296/304     TORQUE-   50-53%                                           Z-3    299/260     FEED SET- 50                                               Z-4    252/316     VACUUM-   203-253 mm Hg                                    Z-5    293/293     MELT TEMP.-                                                                             223° C.                                   Z-6    266/232     RATE-     116 kg/hr                                        Z-7    268/266                                                          Ex. 83                                                                              Z-1    288/285     RPM-      90                                               Z-2    293/272     TORQUE-   50-56%                                           Z-3    299/254     FEED SET- 50                                               Z-4    224/310     VACUUM-   304-329 mm Hg                                    Z-5    266/249     MELT TEMP.-                                                                             226° C.                                   Z-6    266/229     RATE-     122 kg/hr                                        Z-7    268/272                                                          ______________________________________                                    

EXAMPLES 84-87

This example illustrates the use of a graft copolymer of the presentinvention in the preparation of bottles from polypropylene materials.

The graft polymer of Example 69 was blended at various levels up to 5%by weight with either of two commercial polypropylenes used for blowmolding of bottles. The matrix polymer of Example 84 was a propylenerandom copolymer believed to contain 2-4% ethylene, supplied by Fina Oil& Chemical Co., Dallas, Tex., as Fina 7231, mfr=2. The matrix polymer ofExample 86 was a propylene homopolymer, mfr=2, supplied by QuantumChemical, USI Division, Rolling Meadows, Ill. as Norchem 7200GF. Blendswere made by tumbling the resins.

Samples were injection blow molded on a Jomar machine, model 40, (JomarCorporation, Pleasantville, N.J.). The resin blend, in melt form, wasinjected into a four-cavity mold (two cavities being blocked off) over acore pin with an air hole at the end to form an inflatable parison. Themold was heated and was designed to produce a pattern at the far endwhich will allow a cap to be attached after molding. Temperatures of themold were controlled at the bottle neck, bottle walls, and bottlebottom. The parisons were conveyed to a second station where they wereinflated to form the bottle shape, and then to a third station wherethey were cooled and removed. Bottles, which were a 103.5 ml spicebottle, were judged versus non-modified controls for surface gloss,clarity, uniformity of thickness, wall strength, and the like, as wellas to the ease of molding.

                  TABLE XIII                                                      ______________________________________                                        Molding Conditions for Bottles                                                               Temperatures, °C.                                       Example                                                                              Resin   Graft, %  Melt Bottom Wall  Neck                               ______________________________________                                        84     84      --        243  77.7   104   48.9                               85     84      Ex. 69, 5%                                                                              249  82.2   110   48.9                               86     86      --        243  77.7   104   48.9                               87     86      Ex. 69, 5%                                                                              249  82.2   110   48.9                               ______________________________________                                    

When bottles from Example 85 were compared with their controls fromExample 84, a slight improvement in gloss, notable increase in contactclarity, and noticeable improvement in stiffness were observed. Similaradvantages over the control were seen with at a 1% level of the graftpolymer with the matrix resin of Example 84. The clarity effect was notseen with bottles from Example 87 over control Example 86.

For reasons not fully understood, the same additive at 5% wasdeleterious to the formation of bottles from homopolymer or copolymer ofhigher melt flow rate, even with appropriate adjustments in processingtemperatures; much of the problem was associated with poor dispersion ofthe modifier. Such poor dispersion has not been seen in othercompounding, processing or testing operations. Slightly stiffer bottleof improved gloss could be blown with the graft polymer additive at 0.5weight percent, relative to a control with no additive

A pre-blend (Example 73) of 5% graft copolymer with another mfr=2high-impact copolymer yielded bottles with severe materialnon-uniformity. A dry blend of 0.5% graft copolymer with this same resin(the resin of Example 72) gave bottles with improved gloss and contactclarity.

EXAMPLES 88-94

These examples illustrate the utility of a graft polymer of the presentinvention in the preparation of polypropylene foam and foamed sheet. Inthe examples, a homopolymer of polypropylene (Example 72), mfr=2, apre-blend (Example 73) of that polypropylene with amethacrylate//polypropylene graft copolymer, and a mixture of theExample73 pre-blend with 1% talc (designated Example 88) were employed;into all pellets were blended Ampacet 40104 to incorporate a blowingagent. Ampacet blowing agent is a 10%-active, proprietary chemicalblowing agent dispersed in polyethylene. It is supplied by AmpacetCorporation, 250 South Terrace Avenue, Mt. Vernon, N.Y. 10550. When 10parts of Ampacet are blended, there is 1 part proprietary blowing agentin the formulation.

The polymer mixture was processed in a 25.4-mm, single-screw extruderproduced by Killion Extruders Corporation, utilizing a 24:1length/diameter screw of 4:1 compression ratio, and a 1-mm-diameter roddie. Extrusion conditions are summarized below. The unmodified polymerexhibited severe fluctuations in die pressure (6900-12,400 kPa); theblend containing 5 parts of the graft copolymer could be extruded at aconstant die pressure. In both cases good cell uniformity was observed.Uniform larger cells were noted in the graft-polymer-modified blend whenthe amount of active foaming ingredient was increased to 2%. Thepresence of 1% talc in the modified polyolefin produced the best cellstructure and fastest line speed.

Foam densities of the rods were measured according to ASTM StandardMethod D-792, Method A-L. Although the unmodified matrix polymerproduced the lowest-density foam, the modified polymer foams in generalhad a regular foam-cell structure.

The three materials were also processed on a similar line with a 202-mmcast film die and a heated collecting roll to yield foamed sheet; hereno significant differences in processing were seen among the three resinblends. The individual sample preparations and results are shown inTable XXIV below.

                  TABLE XXIV                                                      ______________________________________                                        Type:    Rod     Rod     Rod   Sheet Sheet Sheet                              Sample:  Ex. 89  Ex. 90  Ex. 91                                                                              Ex. 92                                                                              Ex. 93                                                                              Ex. 94                             Polymer of:                                                                            Ex. 72  Ex. 73  Ex. 88                                                                              Ex. 21                                                                              Ex. 73                                                                              Ex. 73                             ______________________________________                                        Talc, wt %                                                                             --      --      1     --    --    --                                 Foaming                                                                       agent, wt %                                                                            1       1       1     1     1     1                                  Extruder rpm                                                                           80      80      80    75    75    75                                 Melt temp.,                                                                            214     208     209   227   227   227                                °C.                                                                    Melt pres-                                                                             70-127  127     140   56    42    42                                 sure, kg/cm.sup.2                                                             Puller speed,                                                                          13      15      23                                                   meters/min                                                                    Sample   0.469   0.664   0.733                                                Density,                                                                      g/cm.sup.3                                                                    ______________________________________                                    

EXAMPLES 95-98

This example illustrates the utility of a graft copolymer ofpolypropylene/methyl methacrylate in the preparation of blownpolypropylene film. Film was blown from the control polypropylenehomopolymer of Example 74, the pre-blend of Example 75 which contained 5weight percent of the graft copolymer of Example 69, and dry blends ofthe propropylene of Example 74 with 1 and with 5 parts of the graftcopolymer of example 69.

Blown film was produced on a Killion blown film line (Killion ExtrudersCo., Cedar Grove, N.J.), which consists of a 25.4-mm, single-screwextruder operating at a melt temperature of about 216° C., a 50-mmspiral mandrel die, air input for producing a bubble, and a Killionvertical-blown-film tower. The blown-film tower contains two nip rollsfor collapsing the bubble and a means for pulling the film through thenip rolls. The die and pull speeds are adjusted to produce film about5.6 mm thick (two thicknesses) and either 108 or 165 mm wide, theblow-up ratios being 2.125 and 3.25 respectively, at respective top nipspeeds of 7.65 and 5.94 meters/minute.

                  TABLE XXV                                                       ______________________________________                                        Film of                                                                       Example    Materials         Thickness                                        ______________________________________                                        Ex. 95     Ex. 74; no GCP    0.051-0.066                                      Ex. 96     Ex. 75; 5% GCP, Cmpd.                                                                           0.056-0.064                                      Ex. 97     Ex. 74; 5% GCP, Dry Blend                                                                       0.051-0.058                                      Ex. 98     Ex. 74; 1% GCP, Dry Blend                                                                       0.051-0.058                                      ______________________________________                                    

Himont 6523, mfr=4, homopolymer polypropylene was blown into0.025-mm-thick film (single layer) as Example 95 (control). The bubblewas sligthly lopsided, and the frostline (onset of crystallization) wasat an angle to the die. A lopsided bubble results in less uniform filmthicknesses.

With 5% of the graft copolymer of Ex. 69 present, the bubble of Example96 was stabilized, the frostline levelled, and the frostline movedcloser to the die. Both 108- and 165-mm, lay-flat films were produced.Although some fluctuation in die pressure was noted when forming thelatter film, it had the most stable bubble.

This increase in bubble stability was also observed with the 1% and 5%dry blends of Examples 97 and 98. No significant differences in filmappearance was observed between the 5% precompounded blends and the dryblends.

The modified films had decreased film see-through clarity. Contactclarity remained unchanged. No difference in edge-roll color wasobserved between modified and unmodified film.

The "openability" of neat and modified film was tested. Although a veryqualitative test (the collapsed film is snapped between the fingers andone feels how well it opens), no difference between the unmodified andmodified resins was observed.

EXAMPLES 99-104

The experiments illustrate the use of the graft polymer of the presentinvention in producing polypropylene cast film. A single-screw extruder,manufactured by Killion co., was equipped with a 3.81-cm screw of 24/1length/diameter ratio, a 20.3-cm×0.635-mm cast film die, a chill rolland a torque winder for the film, was utilized. The extruder melttemperature was 226° C. The melt was extruded through the die and ontothe chill rolls, the take-up speed being adjusted to produce film ofvarious thicknesses. Film thicknesses was measured, as was "neck-in", anundesirable shrinkage of width. Film stiffness and edge roll color weremeasured qualitatively. Film thicknesses were adjusted increasing linespeed of the torque winder and lowering the extruder output by reducingscrew speed.

                  TABLE XXVI                                                      ______________________________________                                        Film of                                                                       Example    Starting Material                                                                            Form                                                ______________________________________                                         Ex. 99    Ex. 74         Unmodified                                          Ex. 100    Ex. 75         Pre-blend; 5% GCP                                   Ex. 101    Ex. 74 and Ex. 69                                                                            Dry Blend; 5% GCP                                   Ex. 102    Ex. 81         Unmodified                                          Ex. 103    Ex. 82         Pre-blend; 1% GCP                                   Ex. 104    Ex. 83         Pre-blend; 5% GCP                                   ______________________________________                                         GCP = graft copolymer of Example 69                                      

Films of the composition of Example 99 were uniform and consistent atthicknesses of from 0.25 mm to below 2.5 mm. Example 100 producedacceptable film of improved edge color and with less film neck-in.Example 101 also produced less neck-in, but did not improve edge color.Both modified versions yielded stiffer films at equivalent thicknessversus the control, allowing the film to be wound more easily. Theopacity of the film increased with the addition of the graft polymer.

With Examples 102 to 104, the neck-in differences were not noted whenthe graft copolymer was present. The films at both 1 and 5 weightpercent graft copolymer were stiffer than the unmodified control(Examples 103 and 104 versus Example 102).

EXAMPLE 105

This example illustrates that biaxially oriented film can be preparedfrom a polypropylene resin containing 5% of the polypropylene/methylmethacrylate graft copolymer. Under the limited conditions tested, whichwere optimum for the unmodified resin, no distinct advantage could beseed for the additive. At identical extrusion and MDO (machine directionorientation) conditions, the modified resins could not achieve andmaintain the line speeds possible with the unmodified resin during theTDO (transverse direction orientation).

The control resin was Example 81, mfr=2.2, high-clarity homopolymermarketed for film use. Pre-compounded resins were Examples 82 and 83,containing respectively 1% and 5% of the graft copolymer of Example 69(under the extrusion conditions, a dry blend of 5 parts graft copolymerof Ex. 69 with the matrix resin of Example 81 gave very poor dispersion,leading to many gels and frequent film breaks). The blends wereprocessed in a 50.8-mm, Davis-Standard single-screw extruder whichconveyed the melt through a 0.48-meter die and onto a 1.02-meter castingroll. An air knife was used to blow the extrudate onto the casting roll.The casting roll rotated through a water bath to completely quench thesheet. The sheet then was conveyed into the MDO, supplied by Marshalland Williams Co., Providence, RI, and comprising a series of heated niprolls, moving at speeds which cause monoaxial orientation.

After the MDO, the film passed through a slitter to cut the film to theproper width and then onto a winder. These rolls were used to feed thefilm into the TDO, which is an oven with three heating zones, rolls forconveying the film forward, and clamps to grip and laterally expand thefilm.

The film from Example 81 (unmodified resin) was drawn both 4.75:1 and5.0:1 in the MDO, and could be drawn 9:1 in the TDO. The unmodified4.75:1 MDO resin could maintain a TDO line speed of 8.69 meters/minute;the unmodified 5.0:1 MDO resin could maintain a line speed of 6.85meters/minute.

The film from Example 82 (1% graft copolymer) could receive a MDO of4.75:1 and TDO of 9:1 and maintain a 6.85-meters/minute TDO line speed.Frequent film breakage was encountered at higher MDO and higher linespeeds. This biaxially oriented film appeared to be slightly more opaquethan the biaxially oriented film from Example 80. No difference betweenthe edge roll colors of film from Examples 81 and 82 was observed forMDO film.

The films from Example 83 received MDO's of 4.75:1, 5.0:1, and 5.25:1 ata TDO of 9:1. The best film was obtained with a line speed of 6.85meters/minute and with the lowest MDO; tearing would occur under morestressed conditions. Films from Example 83 were noticeably more opaqueand the frost line appeared sooner than with the control film of Example81.

EXAMPLE 106

This example illustrates a profile extrusion trial using polypropylenemodified with a graft copolymer of the present invention. A single-screwextruder was equipped with a die and appropriate cooling, pulling, andsizing equipment to form a profile in the shape of a solid rod withhorizontal flanges. The rod diameter was 4.83 cm., flanges 2.67 cm.(extended beyond rod), and flange thickness 1.52 cm. With unmodifiedresin (Tenite 4E11 copolymer, Eastman Chemical, as described in Example78), symmetry was difficult to maintain in the profile without sag ordistortion. When blends of Example 79 and 80 (1 and 5% graft copolymer,respectively) were employed, the maintenance of shape was improved.

EXAMPLE 107

This example illustrates the use of a graft copolymer blend of thepresent invention in the modification of polypropylene to produceimproved plastic tubing. The polymers used were the unmodified resinsand the resins compounded with 5% of the graft copolymer of Ex. 69, asdescribed in Examples 72 to 77.

A 25.4-mm, single-screw Killion Extruder (Killion Extruders Co., CedarGrove, N.J.) was equipped with a screw of 24/1 length/diameter ratio, atubing die with an outer die diameter of 11.4 mm. and a variable innerdiameter, leading to a 0.25-meter-long water trough for cooling, an airwipe, and a puller and cutter. Conditions and observations are shown inTable below. Ovality is the ratio of smallest outer diameter to largestouter diameter, as measured by calipers; a value of 1 means the tube isuniformly round.

When tubing of good ovality was produced from the unmodified resin, themajor effect of the additive was improvement in tubing stiffness. Withthe resin of Example 72, where ovality was difficult to control atacceptable output rates, the modified resin (Example 73) improvedovality as well as stiffness.

                  TABLE XXVII                                                     ______________________________________                                        Tubing Prepared from Polypropylene and Modified Polypropylene                        Melt        Melt      Inner                                                   Temperature,                                                                              Pressure, Diameter                                         Polymer                                                                              °C.  kPa(a)    mm(set) Ovality                                  ______________________________________                                        Ex. 72 217         8270      8.1     0.75                                     Ex. 73 214         6890      8.1      0.88 (b)                                Ex. 74 185         9650      8.1     0.97                                     Ex. 75 197         6890       8.1 (c)                                                                              0.77                                     Ex. 76 184         6890       8.1 (d)                                                                              0.92                                     Ex. 77 180         8270       8.1 (d)                                                                                0.90 (b,e)                             ______________________________________                                         (a)Extrusion rate equivalent for paired unmodified and modified resin.        (b)Modified extrudate tube stiffer.                                           (c)Higher melt temperature required to avoid "sharkish" on tubing.            (d)With this higher mfr resin, reduced melt temperature and higher puller     speed led to tubing of lower outer diameter.                                  (e)Modified tubing more opaque.                                          

EXAMPLES 108-109

This example illustrates the preparation of pre-compounded blendscontaining talc. The talc used is a white, soft, platy talc of particlesize less than 40 μm, known as Cantal MM-45-90 (Canada Talc IndustriesLimited, Madoc, Ontario). It was used at the 20% level. Thepolypropylene used was a homopolymer of mfr=4, known as Himont 6523. Thegraft copolymer was incorporated at the 5-weight-percent level and wasthe graft copolymer of Example 69. The compounding/preparation of thesesamples was carried out on a 30-mm Werner-Pfleiderer co-rotating,twin-screw extruder. The materials were tumble blended prior to thecompounding.

                  TABLE XXVIII                                                    ______________________________________                                        Blend    % Talc    Modifier    Matrix Polymer                                 ______________________________________                                        Example 108                                                                            20 Cantal --          80% Himont 6523                                (control)                                                                     Example 109                                                                            20 Cantal 5% Example  75% Himont 6523                                ______________________________________                                    

The preparative conditions for the blends are given in Table XXIX. Theextruder was operated at 200 rpm, with no vacuum, at rates of 4.5-4.16kg/hour, and 85-86% torque.

                  TABLE XXIX                                                      ______________________________________                                                   Extruder Zone Settings, °C.                                              Example 108 Example 109                                          Zone         set point/actual                                                                          set point/actual                                     ______________________________________                                        Z-1          125/148     125/151                                              Z-2          220/218     220/219                                              Z-3          230/228     230/229                                              Z-4          230/242     230/241                                              Z-5          240/239     240/239                                              Z-6          240/239     240/239                                              Z-7          240/242     240/239                                               Z-8 (die)   225/239     225/239                                              Melt         239         243                                                  ______________________________________                                    

EXAMPLES 110-112

These examples teach the injection moulding of polyproplylene of variouscompositions and melt flow rates, the polypropylenes containing a graftcopolymer of the present invention. In two examples, a 20% loading ofplaty talc is also present.

Polypropylene may be injection molded into useful objects by employing areciprocating-screw, injection-molding machine such as that of ArburgMaschien Fabrik, Lossburg, Federal Republic of Germany, Model221-51-250. In the preparation of test samples, the extruder is equippedwith an ASTM mold which forms the various test pieces. The conditionschosen for molding were unchanged throughout the various matrix andmodified matrix polymers, and no difficulties in molding were noted.Table XXX describes the blends which are molded; Table XXXI teaches themolding conditions; Table XXXII reports modulus values, Table XXXIIIDynatup impact data, and Table XXXIV heat distortion temperature valuesfo the modified polymers and their controls.

In the following list of injection-molded polymers and blends, allsamples contain 1 or 5 weight percent of the graft copolymer of Example69. The polypropylene matrix resins are described in earlier examples;HP is homopolymer, CP is copolymer, the number is the mfr value. Theblends with talc are described in Examples 108 and 109. All materialswere pre-blended in the melt, except where a dry blend from powder wasdirectly molded. (C) is an unmodified control; (CT) is a control withtalc, but no graft copolymer.

All test methods were by ASTM standard methods: flexural modulus andstress are by ASTM Standard Method D 790, heat distortion temperatureunder load is by ASTM Standard Method D 648 and Dynatup impact is byASTM Standard Method D 3763.

Table XXX also includes the melt flow rates (mfr) for the unmodified andpre-compounded blends. In most cases, the melt flow rate is unchanged orslightly decreased in the presence of the graft copolymer, so that themelt viscosity under these intermediate-shear conditions is notextensively increased. The melt flow rate is by ASTM Standard MethodD-1238, condition L (230° C., 298.2 kPa) and has units of gramsextruded/10 minutes.

                  TABLE XXX                                                       ______________________________________                                        Example                                                                              Matrix  Graft, % Talc, %                                                                              Dry-Blend?                                                                            mfr                                    ______________________________________                                         74 (C)                                                                              HP, 4   --       --     --      4.40, 4.06                             75     HP, 4   5        --     --      6.07                                   110    HP, 4   5        --     YES                                            108 (CT)                                                                             HP, 4   --       20     --                                             109    HP, 4   5        20     --                                             76 (C) CP, 4   --       --     --      4.47                                   77     CP, 4   5        --     --      3.75                                   111    CP, 4   5        --     YES                                            72 (C) CP, 2   --       --     --      2.37                                   73     CP, 2   5        --     --      2.02                                   112    CP, 2   5        --     YES                                            78 (C) CP      --       --     --      2.92                                   79     CP      1        --     --      2.04                                   80     CP      5        --     --      2.12                                   81 (C) CP      --       --     --      2.33                                   82     CP      1        --     --      3.81                                   83     CP      5        --     --      2.16                                   ______________________________________                                    

                  TABLE XXXI                                                      ______________________________________                                        Injection Molding Conditions for Propylene                                    ______________________________________                                        Cylinder temperatures, °C.                                                               (setting/measured)                                          Feed        -216/216  Metering    -216/216                                    Compression -216/216  Nozzle       216/216                                    Mold Temperatures, °C.                                                 Stationary  -49/49    Moveable    -49/49                                      Cycle time, seconds                                                           Injection forward                                                                         -14       Mold Open   -0.5                                        Cure        -14       Total Cycle -0.5                                        Mold Closed -1.2                                                              Machine readings:                                                             Screw speed (rpm) - 400                                                       Back pressure (kPa) - 172                                                     Injection (1st stage) (kPa) - 861                                             ______________________________________                                    

The flexural modulus data from Table XXXII indicate the stiffeningeffect of the graft copolymer. Results are in megapascals (mPa).

                  TABLE XXXII                                                     ______________________________________                                                      FLEXURAL   STRESS                                                             MODULUS    (at max)                                             Example       mPa        mPa                                                  ______________________________________                                        74 (C)        1470.6     43.8                                                 75            1744.4     47.5                                                 110           1783.1     46.9                                                 108 (CT)      2768.0     52.0                                                 109           2867.0     54.5                                                 ______________________________________                                    

Table XXXIII summarizes Dynatup impact data (in Joules) at varioustemperatures for the blends and controls tested. The data indicate, ingeneral, slightly improved impact for the pre-blended materials, adeterioration in impact strength on molding dry blends of graftcopolymer and matrix polymer, and an increase in impact strength for thetalc-modified blend also containing the graft copolymer.

                  TABLE XXXIII                                                    ______________________________________                                        Dynatup Impact (joules) at                                                    Test Temperature, °C.                                                  Example 23          15       5       -5                                       ______________________________________                                        74   (C)     4.9 ± 2.7                                                                             4.4 ± 1.5                                                                         3.8 ± 0.3                                                                          2.6 ± .41                           75           5.7 ± 3.4                                                                             4.6 ± 0.8                                                                         2.7 ± 1.5                                                                           3.4 ± 1.09                         110          3.4 ± 1.1                                                                             2.0 ± 0.5                                                                         1.9 ± 1.0                                                                          1.5 ± .41                           108  (CT)    3.0 ± 0.5                                                                             3.4 ± 0.8                                                                         4.2 ± 1.6                                                                          5.0 ± 2.5                           109          1.9 ± 0.5                                                                             4.1 ± 2.3                                                                         4.8 ± 1.8                                                                          5.0 ± 2.5                           76   (C)    40.0 ± 0.5                                                     77          43.9 ± 0.4                                                     111         14.0 ± 6.4                                                     72   (C)    37.9 ± 1.8                                                     73           43.1 ± 10.3                                                   112         32.4 ± 9.5                                                     78   (C)    36.7 ± 0.4                                                     79          36.3 ± 1.1                                                     80          37.1 ± 0.7                                                     81*  (C)     13.3 ± 10.7                                                                           --     3.3 ± 0.8                                                                          2.7 ± 0.2                           82           4.9 ± 0.7                                                                             --     3.0 ± 1.4                                                                          3.0 ± 0.8                           83           7.6 ± 3.7                                                                             --     3.3 ± 0.8                                                                          3.5 ± 1.1                           ______________________________________                                         *The large standard deviation at room temperature is suspect.            

Table XXXIV presents heat distortion and hardness values for one series.The modified polymer appears to exhibit a slightly higher heatdistortion temperature and hardness, although there are inconsistenciesnoted. The Rockwell hardness values represent separate determinations ontwo samples of the material from the indicated example.

                  TABLE XXXIV                                                     ______________________________________                                        Heat Deflection Temperature                                                   at 2° C./Minute at                                                                            Rockwell Hardness                                      Example 411 kPa    1645 kPa    "C" Scale                                      ______________________________________                                        74   (C)    110.9      61.0      58.4   56.5                                  75          113.8      63.3      60.7   59.3                                  110         117.3      68.7      57.9   46.9                                  108  (CT)   128.2      76.8      57.3   64.7                                  109         124.7      81.9      65.4   63.7                                  ______________________________________                                    

EXAMPLE 113

This examples illustrates the effect of the molecular weight of thepolypropylene trunk component of the graft copolymer on the sagmodification of polypropylenes of various molecular weights. Graftcopolymers were prepared from polypropylene of various melt flow rates.All modifiers were prepared as in Example 58. The 35 mfr polypropylene(Himont PD-701) was run at 65% solids. The 12 mfr polypropylene (HimontPro-fax 6323) was run at 60% solids. The 4 mfr polypropylene (HimontPro-fax 6523) and the 0.8 mfr polypropylene (Himont Pro-fax 6723) wererun at 55% solids. The molecular weights for the polypropylene baseresins, where known, are given in Table XXXV, below.

These were evaluated as melt strength improvers at 4% by weight inseveral of these same polypropylenes. Standard mill and press conditionswere used for all blends, except the 0.8 mfr/0.8 mfr polypropyleneblends which were milled at 215° C. and pressed at 215° C. Sag rateswere measured by the standard procedures. The sag slope at 190° C. isreported in Table XXXVI, below.

                  TABLE XXXV                                                      ______________________________________                                        MW-MFR Data for Polypropylene Base Resin                                      Molecular-Weight                                                                          Weight-Average Molecular Weight × 10.sup.5                  Source      12 mfr PP  4 mfr PP   0.8 mfr PP                                  ______________________________________                                        (a)         3          4.3        7.1                                         (b)         2.45       3.05       3.5, 4.7                                    (c)         0.27*      0.45*      --                                          ______________________________________                                         Source of MolecularWeight Value:                                              (a) Supplier's data.                                                          (b) Sheehan et al, J. Appl. Polymer Sci., 8, 2359 (1964).                     (c) Mays et al, ibid., 34, 2619 (1987).                                       *These values are numberaverage molecular weight.                        

                  TABLE XXXVI                                                     ______________________________________                                        Sag Slope at 190 °  C. for Olefin Blends (min.sup.-1)                           polypropylene base resin (96%)                                                  35                                                                 modifier (4%)                                                                            mfr PP  12 mfr PP  4 mfr PP                                                                             0.8 mfr PP                               ______________________________________                                        none       1.6     0.52       0.25   0.099                                    35 mfr PP based                                                                          1.8     0.52       0.23   0.074                                    12 mfr PP based                                                                          1.2     0.41       0.034  <0.02                                    4 mfr PP based                                                                           1.0     0.16       0.022  <0.02                                    0.8 mfr PP based                                                                         0.64    0.16       0.031  <<0.02                                   ______________________________________                                    

In all cases except where a high-melt-flow base resin was modified witha graft polymer having a trunk of high-flow-rate (low-molecular-weight)polypropylene, sag improvement was observed. The molecular weight forthe resin of mfr=35 is not accurately known; it is believed to be madeby thermal/oxidative processing of a higher molecular weight resin. Sucha process would both lower the molecular weight and narrow theoriginally broad molecular weight distribution.

EXAMPLE 114

This example illustrates the effectiveness of the graft copolymes of thepresent invention as compatibilizing agents for polymers that areotherwise poorly compatible. In this example of a polyolefin, a polarpolymer, and the graft copolymer of the present invention werecompounded in an intermeshing, co-rotating, twin-screw extruder(Baker-Perkins MPC/V 30) with a screw length-to-diameter ratio of 10:1.The compounder was run at 200 rpm and temperatures were adjusted toaccommodate the polymers in the blend and achieve a good melt. The melttemperature in the compounding zone is recorded in the second column ofthe table. The melt was fed directly to a 38-mm, single-screw,pelletizing extruder with a length-to-diameter ratio of 8:1. The melttemperature in the transition zone between the compounding and thepelletizing extruder is shown in column 3 of Table XXXVIII, below. Themelt was extruded into strands through a die, cooled in a water bath,and cut into pellets.

Table XXXVII below summarizes the polymerw which were used in the blendsof the present example, while Table XXXIX shows that the graft copolymerhas little effect upon the tensile strength of the unblended polymers,that is, it does not act to a significant degree as a toughening agent.In the subsequent tables, Tables XL and XLI, improvement in tensilestrength of the blended polymers indicates an increase in compatabilityof the blended polymers with one another in the presence of the graftcopolymers of the present invention.

Under the proper compounding conditions, an increase in compatibilitymay also produce a decrease in the size of polymer domains in the blend.Scanning electron microscopy confirms that in some of these examples,significant domain-size reductions occur when the graft copolymer isadded. For example, the polypropylene domains average 2 micrometers inthe 70 PMMA/30 PP blend of example 114. The addition of 5 phrcompatibilizer reduced the domain size to 0.5 μm. The addition of 15 phrcompatibilizer reduced the domain size to 0.43 μm. Although not all ofthe domain sizes were reduced, several others were reduced by 10-30% bythe addition of 5 phr compatibilizer. This is a further suggestion thatthe compatibilizer is acting on the interface of the polymer domainsrather than on the individual polymers.

Table XLI summarizes the compatibilizing effect of the graft copolymersupon the various polymer blends.

                                      TABLE XXXVII                                __________________________________________________________________________    Polymers Used in the Blend Examples                                                                           Other                                         Polymer and Designation                                                                          Grade    Spec.                                                                             Specifi-                                      in Tables    Producer                                                                            Designation                                                                            Grav.                                                                             cations                                       __________________________________________________________________________    SAN          Monsanto                                                                            Lustran SAN 33                                                                         1.07                                                                              mfr = 14                                      Styrene-Acrylonitrile           ASTM D 1238                                   Polymer                         Cond. (I)                                     PA66         DuPont                                                                              Zytel 101                                                                              1.14                                                                              mp = 255° C.                           Nylon 6.6                       (D2117)                                       PET          Eastman                                                                             Kodapak PET                                                                            1.4 mp = 245° C.                           Polyethylene Kodak 7352         (DSC),                                        Terephthalate                   iv = 0.74                                     EVOH         EVAL Co.                                                                            Eval EP-E105                                                                           1.14                                                                              44 moles % E,                                 Ethylene Vinyl                                                                             of America         mp = 164 C,                                   Alcohol Copolymer               mfr = 5.5                                                                     (190° C.,                                                              2160 g)                                       PC           General                                                                             Lexan 121                                                                              1.20                                                                              mfr = 16.5                                    Polycarbonate                                                                              Electric           ASTM D 1238                                                Plastics           Cond. (O)                                     PVC          Georgia                                                                             SP-7107  1.35                                              Polyvinyl Chloride                                                                         Gulf Corp.                                                       PMMA         Rohm and                                                                            Plexiglas VM                                                                           1.18                                                                              mfr = 15                                      Poly (Methyl Haas Co.                                                         Methacrylate)                                                                 EP           Exxon Vistalon 719                                                                           0.89                                                                              54 Mooney                                     Ethylene Propylene              (D-1646)                                      Copolymer                                                                     HDPE         Phillips                                                                            Marlex   0.950                                                                             mfr = 4                                       High-Density 66 Co.                                                                              HMN 5060                                                   Polyethylene                                                                  PP           Himont                                                                              Pro-fax 6523                                                                           0.903                                                                             mfr = 4                                       Polypropylene                                                                 EVA          DuPont                                                                              Elvax 650                                                                              0.933                                                                             12% VA                                        Ethylene Vinyl Acetate          mfr = 8                                       LLDPE        Exxon Escorene 0.926                                                                             mfr = 12                                      Linear Low-Density LL-6202                                                    Polyethylene                                                                  PS           Huntsman                                                                            PS-203   1.06                                                                              mfr = 8                                       Polystyrene  Chemical                                                                            (crystal)                                                  PBT          General                                                                             Valox 6120                                                 Poly(butylene                                                                              Electric                                                         terephthalate)                                                                PA6          Allied                                                                              Capron 8253                                                                            1.09                                                                              mp = 21° C.                            Nylon 6      Signal                                                           ABS          Dow   Magnum 341                                                                             1.05                                                                              mfr = 5                                       Acrylonitrile-                                                                             Chemical                                                         Butadiene-Styrene                                                             Resin                                                                         PC/PBT       General                                                                             Xenoy 1101                                                                             1.21                                              Polycarbonate/                                                                             Electric                                                         Poly(butylene tere-                                                           phthalate alloy                                                               __________________________________________________________________________

                  TABLE XXXVIII                                                   ______________________________________                                                    melt temperatures (°C.)                                                compounder                                                                             transition                                               ______________________________________                                        PMMA          225-235    210-220                                              SAN           220-230    210-220                                              EVOH          205-225    200-215                                              PA66          260-275    255-270                                              PET           245.275    245-255                                              PVC           205-230    190-215                                              PC            250-290    240-270                                              ______________________________________                                    

The pellets were dried and injection molded on a reciprocating-screwinjection molding machine (New Britain Model 75) into test specimens.

                  TABLE XXXIX                                                     ______________________________________                                        Effect of Compatibilizer on Polymer Tensile Strength                          Tensile Strengths Shown in MegaPascals (MPa)                                  compatibilizer concentration                                                  Polymer   0 phr         5 phr  15 phr                                         ______________________________________                                        PMMA      65.44         64.79  61.27                                          SAN       71.91         62.74  55.89                                          EVOH      68.78         66.21  63.78                                          PA66      64.82         64.68  66.60                                          PET       58.26         59.33  59.72                                          PVC       45.25         44.97  45.22                                          PC        62.63         63.05  63.70                                          HDPE      22.59         22.66  24.14                                          PP        33.02         34.03  33.95                                          EP         4.79          5.50   5.84                                          LLDPE     10.91         11.80  12.99                                          EVA        8.64          8.67   8.17                                          ______________________________________                                    

                                      TABLE XL                                    __________________________________________________________________________    Tensile Strengths (MPa) of Blends of Polyolefins and Polar Polymers           polar                                                                              30% polar polymer                                                                        55% polar polymer                                                                        80% polar polymer                                  polymer                                                                            0 phr                                                                             5 phr                                                                            15 phr                                                                            0 phr                                                                             5 phr                                                                            15 phr                                                                            0 phr                                                                             5 phr                                                                            15 phr                                      __________________________________________________________________________    HDPE                                                                          *PMMA                                                                              25.26                                                                             27.00                                                                            30.26                                                                             31.42                                                                             38.30                                                                            39.54                                                                             50.78                                                                             53.77                                                                            55.55                                       *SAN 25.77                                                                             28.09                                                                            30.57                                                                             34.71                                                                             41.51                                                                            38.33                                                                             51.88                                                                             55.08                                                                            51.23                                       *EVOH                                                                              26.57                                                                             26.80                                                                            27.74                                                                             33.18                                                                             38.00                                                                            39.58                                                                             49.24                                                                             51.32                                                                            50.79                                       PA66 26.94                                                                             28.85                                                                            29.72                                                                             38.34                                                                             38.11                                                                            38.33                                                                             61.22                                                                             65.62                                                                            69.23                                       PET  25.97                                                                             28.61                                                                            30.98                                                                             37.70                                                                             37.93                                                                            40.09                                                                             50.23                                                                             51.72                                                                            50.91                                       PVC  20.89                                                                             22.92                                                                            24.86                                                                             19.91                                                                             23.67                                                                            27.34                                                                             26.18                                                                             30.72                                                                            34.87                                       PC   25.66                                                                             28.80                                                                            30.93                                                                             31.11                                                                             35.20                                                                            38.53                                                                             55.61                                                                             50.41                                                                            51.92                                       PP                                                                            *PMMA                                                                              34.02                                                                             35.37                                                                            37.81                                                                             40.23                                                                             43.45                                                                            45.84                                                                             46.40                                                                             53.70                                                                            56.6                                        *SAN 33.67                                                                             38.76                                                                            41.05                                                                             37.67                                                                             47.65                                                                            46.08                                                                             41.11                                                                             54.12                                                                            51.81                                       *EVOH                                                                              32.85                                                                             37.40                                                                            38.56                                                                             35.01                                                                             44.65                                                                            45.60                                                                             42.73                                                                             53.38                                                                            52.57                                       PA66 32.06                                                                             40.29                                                                            40.38                                                                             42.72                                                                             52.17                                                                            51.10                                                                             64.71                                                                             67.84                                                                            66.15                                       PET  32.93                                                                             33.80                                                                            35.15                                                                             39.47                                                                             43.81                                                                            43.64                                                                             37.67                                                                             53.12                                                                            54.04                                       PVC  36.32                                                                             37.68                                                                            39.35                                                                             35.28                                                                             37.87                                                                            40.79                                                                             30.88                                                                             40.00                                                                            42.56                                       PC   33.82                                                                             36.68                                                                            39.09                                                                             36.69                                                                             40.13                                                                            44.64                                                                             42.38                                                                             46.24                                                                            51.64                                       EP                                                                            PMMA 8.20                                                                              10.87                                                                            12.51                                                                             19.99                                                                             24.17                                                                            27.81                                                                             42.47                                                                             44.59                                                                            46.93                                       SAN  8.10                                                                              12.53                                                                            14.11                                                                             22.14                                                                             28.82                                                                            28.15                                                                             45.92                                                                             50.68                                                                            44.58                                       EVOH 12.19                                                                             12.04                                                                            11.69                                                                             24.92                                                                             24.66                                                                            23.17                                                                             41.29                                                                             42.39                                                                            42.70                                       PA66 13.04                                                                             13.04                                                                            12.36                                                                             27.62                                                                             27.98                                                                            26.33                                                                             40.87                                                                             48.77                                                                            43.48                                       PET  7.94                                                                              8.40                                                                             11.13                                                                             20.22                                                                             20.43                                                                            22.27                                                                             33.72                                                                             37.00                                                                            38.87                                       PVC  6.17                                                                              9.05                                                                             12.88                                                                             12.93                                                                             18.28                                                                            19.22                                                                             25.50                                                                             28.41                                                                            30.60                                       PC   10.31                                                                             12.05                                                                            13.66                                                                             23.10                                                                             24.34                                                                            25.60                                                                             40.18                                                                             41.79                                                                            42.76                                       LLDPE                                                                         PMMA 15.23                                                                             18.63                                                                            20.90                                                                             24.88                                                                             30.68                                                                            32.84                                                                             48.95                                                                             55.36                                                                            54.14                                       SAN  15.78                                                                             21.08                                                                            22.57                                                                             26.50                                                                             35.76                                                                            36.71                                                                             47.52                                                                             56.92                                                                            48.84                                       EVOH 16.83                                                                             17.26                                                                            18.26                                                                             30.02                                                                             31.74                                                                            31.87                                                                             51.83                                                                             50.71                                                                            52.29                                       PA66 17.93                                                                             17.99                                                                            19.98                                                                             29.67                                                                             28.49                                                                            25.23                                                                             64.65                                                                             67.55                                                                            67.26                                       PET  15.33                                                                             18.09                                                                            20.35                                                                             25.53                                                                             28.23                                                                            30.78                                                                             45.02                                                                             46.16                                                                            42.87                                       PVC  14.72                                                                             14.12                                                                            15.73                                                                             12.45                                                                             18.09                                                                            20.50                                                                             25.99                                                                             30.54                                                                            33.69                                       PC   13.64                                                                             19.20                                                                            18.48                                                                             19.22                                                                             27.83                                                                            30.46                                                                             38.45                                                                             40.59                                                                            38.86                                       EVA                                                                           PMMA 10.57                                                                             11.28                                                                            14.38                                                                             23.06                                                                             21.10                                                                            28.31                                                                             45.99                                                                             47.02                                                                            50.87                                       SAN  12.40                                                                             13.62                                                                            15.22                                                                             27.97                                                                             27.29                                                                            29.35                                                                             48.94                                                                             52.01                                                                            46.14                                       EVOH 13.13                                                                             13.97                                                                            16.59                                                                             32.41                                                                             28.65                                                                            35.43                                                                             50.97                                                                             50.28                                                                            48.81                                       PA66 14.15                                                                             13.54                                                                            14.42                                                                             27.36                                                                             24.59                                                                            26.92                                                                             40.75                                                                             38.35                                                                            31.60                                       PET  14.55                                                                             14.35                                                                            12.31                                                                             21.22                                                                             23.90                                                                            26.45                                                                             43.20                                                                             43.91                                                                            48.44                                       PVC  7.69                                                                              8.28                                                                             10.25                                                                             13.40                                                                             14.29                                                                            18.17                                                                             19.22                                                                             23.76                                                                            28.12                                       PC   14.05                                                                             14.54                                                                            13.52                                                                             19.78                                                                             21.79                                                                            24.85                                                                             39.26                                                                             40.55                                                                            41.46                                       __________________________________________________________________________     *polar polymer levels are 20, 45, and 70% instead of 30, 55 and 80%.     

                  TABLE XLI                                                       ______________________________________                                        Effect of Compatibilizer on Tensile Strength of Blends of                     Polyolefins and Polar Polymers                                                Increase in                                                                   Tensile Strength (MPa) from the Compatibilizer                                                     55%         80%                                          polar  30% polar polymer                                                                           polar polymer                                                                             polar polymer                                polymer                                                                              5 phr    15 phr   5 phr 15 phr                                                                              5 phr 15 phr                             ______________________________________                                        HDPE                                                                          PMMA   1.74     5.01     7.38  8.12  2.99  4.77                               SAN    2.32     4.80     6.80  3.63  3.21  -0.64                              *EVOH  0.23     1.17     4.81  6.39  2.08  1.54                               PA66   1.90     2.77     -0.23 -0.01 4.40  8.00                               PET    2.65     5.01     0.23  2.39  1.48  0.68                               PVC    2.03     3.97     3.76  7.43  4.54  8.69                               PC     3.14     5.27     4.10  7.42  -5.20 -3.69                              PP                                                                            *PMMA  1.35     3.79     3.22  5.61  7.29  10.22                              SAN    5.09     7.38     9.98  8.41  13.02 10.70                              *EVOH  4.56     5.72     9.64  10.59 10.65 9.83                               PA66   8.23     8.32     9.45  8.38  3.13  1.44                               PET    0.86     2.22     4.34  4.17  15.44 16.37                              PVC    1.36     3.03     2.59  5.51  9.11  11.68                              PC     2.86     5.27     3.43  7.94  3.85  9.26                               EP                                                                            PMMA   2.66     4.30     4.18   7.82 2.12  4.46                               SAN    4.43     6.01     6.68  6.01  4.76  -1.34                              EVOH   -0.15    -0.50    -0.27 -1.75 1.10  1.41                               PA66   0.01     -0.68    0.36  -1.29 7.90  2.61                               PET    0.46     3.19     0.21  2.05  3.29  5.16                               PVC    2.86     6.71     5.35  6.29  2.91  5.10                               PC     1.74     3.35     1.24  2.50  1.61  2.59                               LLDPE                                                                         PMMA   3.40     5.67     5.80  7.96  6.42  5.19                               SAN    5.31     6.80     9.26  10.21 9.40  1.32                               EVOH   0.43     1.43     1.72  1.85  -1.12 0.45                               PA66   0.06     2.05     -1.19 -4.44 2.90  2.61                               PET    2.76     5.01     2.70  5.25  1.14  -2.14                              PVC    -0.59    1.01     5.64  8.05  4.56  7.70                               PC     5.56     4.85     8.61  11.24 2.14  0.41                               EVA                                                                           PMMA   0.71     3.81     -1.95 5.25  1.03  4.87                               SAN    1.22     2.81     -0.68 1.38  3.07  -2.80                              EVOH   0.83     3.45     -3.75 3.02  -0.68 -2.16                              PA66   -0.61    0.27     -2.77 -0.44 -2.40 -9.15                              PET    -0.20    -2.25    2.68  5.23  0.70  5.24                               PVC    0.59     2.56     0.89  4.76  4.54  8.89                               PC     0.49     -0.53    2.01  5.07  1.30  2.20                               ______________________________________                                         *polar polymer levels are 20. 45 and 70% instead of 30, 55 and 80%.      

                  TABLE XLII                                                      ______________________________________                                        Compatibilization Effect                                                      HDPE         PP       EP       LLPDE  EVA                                     ______________________________________                                        PMMA    +++      +++.sup.1                                                                              +++    +++    +++                                   SAN     +++      +++      +++    +++    ++                                    EVOH    ++       +++.sup.1                                                                              0      0      ++                                    PA66    ++       +++.sup.1                                                                              +      +      0                                     PET     +        ++.sup.1 ++     ++     ++                                    PVC     +++      +++      +++    ++.sup.1                                                                             ++                                    PC      ++       +++.sup.1                                                                              +      ++     +                                     ______________________________________                                         +++ - compatibilization at all three polyolefinpolar polymer ratios (not      necessarily at all compatibilizer levels)                                     ++ - compatibilization at two of the three polyolefinpolar polymer levels     + - compatibilization at one of the two polyolefinpolar polymer levels        0  no compatibilization seen at any polyolefinpolar polymer ratio, at any     compatibilizer level                                                          .sup.1 additional evidence for compatibilization in the reduction of          domain size by 10-80%                                                    

EXAMPLE 115

The compatibilizing effect on selected, additional polymer pairs wasevaluated in the following example. The blends were compounded, moldedand tested for tensile strength as previously described. The results inTable XLIII again indicate that the compatibilizer has minimal or anegative effect on the polar polymers, but a positive effect on thepolar/nonpolar polymer blends. A large tensile strength improvement isseen for the ABS/PP blend. Smaller but significant improvements are seenfor the blends of PP with PA6 and with PC/PBT. With the PS blendsevaluated the effect was negligible.

                  TABLE XLIII                                                     ______________________________________                                                  tensile strengths (MPa)                                                                      polar                                                                         polymer +     blend.sup.1 +                                                   15 phr        15 phr                                 polar  nonpolar polar    graft         graft                                  polymer                                                                              polymer  polymer  copolymer                                                                             blend.sup.1                                                                         copolymer                              ______________________________________                                        PBT    PP       43.02    45.11   36.96 38.96                                  PA6    PP       56.11    51.67   43.50 47.04                                  PS     PP       45.26    40.45   38.88 37.36                                  PS     HDPE     45.26    40.45   36.48 33.76                                  ABS    PP       51.25    52.25   32.25 42.55                                  PC/PBT PP       51.77    51.79   38.99 41.88                                  ______________________________________                                         .sup.1 blend in all cases refers to 55 parts by weight polar polymer and      45 parts by weight nonpolar polymer.                                     

The effect of the graft copolymer on multi-component blends such asthose representative of commingled scrap polymers are shown in TableXLIV. In all cases a significant increase in tensile strength isobserved when the compatibilizer is present.

                  TABLE XLIV                                                      ______________________________________                                        Compatibilization of Multicomponent Blends                                                                        Tensile                                   Polar Polymers                                                                          Nonpolar Polymers                                                                            Compati-   Strength                                  PS  PET    PVC    HDPE  LLDPE  PP  bilizer  (MPa)                             ______________________________________                                        12  7      5      33.5  33.5    9  none     16.27                             12  7      5      33.5  33.5    9   5       17.67                             12  7      5      33.5  33.5    9  15       21.77                             12  8      --     35    35     10  none     18.62                             12  8      --     35    35     10   5       19.98                             12  8      --     35    35     10  15       22.16                             12  --     6      36    36     10  none     17.06                             12  --     6      36    36     10   5       19.21                             12  --     6      36    36     10  15       21.91                             ______________________________________                                    

EXAMPLE 116

This example further illustrates compatibilization of polymer blendsusing graft copolymers of the present invention.

Blends of ethylene-vinyl alcohol copolymer (Kuraray EP-F101A),polypropylene (Himont 6523) and graft copolymer were milled on a7.62-cm×17.78-cm electric mill at 204° C. to flux plus three minutes.The stocks were pressed at 204° C. and 103 MPa for three minutes (CarverPress, 12.7-cm×12.7-cm×3.175-mm mold) and at room temperature and 103MPa for three minutes. Two graft copolymers were used in this example.The first (Graft Copolymer A) was a polypropylene-acrylic graftcopolymer prepared from mfr=4 polypropylene homopolymer (100 parts) anda 93:2:5 mixture of methyl methacrylate:ethyl acrylate:methacrylic acid(100 parts). Polymerization was done in Isopar E solvent at 160° C. at50% solids over one hour with a di-t-butyl peroxide radical flux of0.00012. The product isolated contained 44% acrylate. The second graftcopolymer (Graft Copolymer B) was a polypropylene-acrylic graftcopolymer prepared from mfr=4 propylene homopolymer (100 parts) and a95:5 mixture of methyl methacrylate:ethyl acrylate (150 parts).Polymerization was done in Isopar E solvent at 155° C. at 60% solids.The feed time was 60 minutes and the radical flux was 0.00010. Theproduct contained 53% acrylate. Addition of the graft copolymer resultsin an increase in tensile strength and modulus.

                  TABLE XLV                                                       ______________________________________                                        Compatibilzation of EVOH and Polypropylene                                                              notched                                                             graft     Izod   tensile                                                                              tensile                               EVAL   PP       copolymer tensile                                                                              strength                                                                             modulus                               (grams)                                                                              (grams)  (grams)   (J/m)  (MPa)  (MPa)                                 ______________________________________                                        90     30       0         21     29.85  2570                                  90     25       5.sup.1   21     48.06  3190                                  90     25       5.sup.2   22     46.75  3270                                  30     90       0         18     21.37  1930                                  30     75       15.sup.1  18     29.79  2140                                  30     75       15.sup.2  13     30.41  2030                                  ______________________________________                                         1  Graft Copolymer A (see text above).                                        2  Graft Copolymer B (see test above).                                   

While the invention has been described with reference to specificexamples and applications, other modifications and uses for theinvention will be apparent to those skilled in the art without departingfrom the spirit and scope of the invention defined in the appendedclaims.

What is claimed is:
 1. A graft copolymer capable of imparting to apolyolefin when blended therewith a relatively high tensile modulus andhigh resistance to sagging without increasing melt viscosity, thecopolymer comprising:(a) a non-polar polyolefin trunk selected from thegroup consisting of polyethylene, polypropylene, polybutylene,poly(4-methylpentene), copolymers of said olefins with each other, andone or more copolymers of said olefins with minor amounts of 1-alkenes,vinyl esters, vinyl chloride, (meth)acrylic ester, and (meth)acrylicacid, said trunk having a Mw of between about 50,000 and 1,000,000; and(b) at least one methacrylate chain grafted with a covalent bond to saidtrunk having a weight ratio with said trunk of from about 1:9 to about4:1, said chain being a polymer derived from at least about 80% of amonomer of a methacrylic ester of the formula CH₂ =C(CH₃)COOR, where Ris alkyl, aryl, substituted alkyl, substituted aryl, or substitutedalkaryl, and less than about 20% of an acrylic or styrenic monomercopolymerizable with the methacrylic ester, said chain having a Mw offrom about 20,000 to 200,000.
 2. A copolymer as claimed in claim 1wherein the weight average molecular weight of the methacrylate chain isbetween about 30,000 and 150,000.
 3. A copolymer as claimed in claim 1wherein the molecular weight of the trunk is about 100,000 to 400,000.4. A copolymer as claimed in claims 1, 3 or 5 wherein the methacrylicester is methyl methacrylate.
 5. A copolymer as claimed in claims 1, 3or 5 wherein the polyolefin trunk is polypropylene.
 6. A copolymer asclaimed in claims 1, 3 or 5 wherein the polyolefin trunk ispolypropylene and the methacrylate chain is a methyl methacrylatepolymer.
 7. The graft copolymer of claim 1 wherein the substituted alkylgroup is alkylthioalkyl.
 8. The graft copolymer of claim 7 wherein thealkylthioalkyl group is ethylthioethyl.